Garbage collection of expired snapshots

ABSTRACT

Methods and systems for reclaiming disk space via consolidation and deletion of expired snapshots are described. The expired snapshots may comprise snapshots of a virtual machine that are no longer required to be stored within a data storage domain (e.g., a cluster of data storage nodes or a cloud-based data store). In some cases, rather than storing an incremental file corresponding with a particular snapshot of the virtual machine, a full image of the particular snapshot may be generated and stored within the data storage domain. The generation of the full image may allow a chain of dependencies supporting the expired snapshots to be broken and for the expired snapshots to be deleted or consolidated. The full image of the particular snapshot may be generated using compute capacity in the cloud or may be generated locally by a storage appliance and uploaded to the data storage domain.

BACKGROUND

Virtualization allows virtual hardware to be created and decoupled fromthe underlying physical hardware. For example, a hypervisor running on ahost machine or server may be used to create one or more virtualmachines that may each run the same operating system or differentoperating systems (e.g., a first virtual machine may run a Windows®operating system and a second virtual machine may run a Unix-likeoperating system such as OS X®). A virtual machine may comprise asoftware implementation of a physical machine. The virtual machine mayinclude one or more virtual hardware devices, such as a virtualprocessor, a virtual memory, a virtual disk, or a virtual networkinterface card. The virtual machine may load and execute an operatingsystem and applications from the virtual memory. The operating systemand applications executed by the virtual machine may be stored using thevirtual disk. The virtual machine may be stored (e.g., using a datastorecomprising one or more physical storage devices) as a set of filesincluding a virtual disk file for storing the contents of the virtualdisk and a virtual machine configuration file for storing configurationsettings for the virtual machine. The configuration settings may includethe number of virtual processors (e.g., four virtual CPUs), the size ofa virtual memory, and the size of a virtual disk (e.g., a 10 GB virtualdisk) for the virtual machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts one embodiment of a networked computing environment.

FIG. 1B depicts one embodiment of a server.

FIG. 1C depicts one embodiment of a storage appliance.

FIG. 1D depicts one embodiment of a portion of an integrated datamanagement and storage system that includes a plurality of nodes incommunication with each other and one or more storage devices.

FIGS. 2A-2Q depict various embodiments of sets of files and datastructures associated with managing and storing snapshots of virtualmachines.

FIG. 3A is a flowchart describing one embodiment of a process formanaging and storing virtual machine snapshots using a data storagesystem.

FIG. 3B is a flowchart describing one embodiment of a process fordetermining the type of snapshot to be stored using a data storagesystem.

FIG. 3C is a flowchart describing one embodiment of a process forrestoring a version of a virtual machine using a data storage system.

FIGS. 4A-4D depict various embodiments of electronic files stored withina first storage domain (Domain A) and a second storage domain (DomainB).

FIGS. 4E-4J depict various embodiments of electronic files stored withina first storage domain (Domain A).

FIG. 5A is a flowchart describing one embodiment of a process forreclaiming disk space within an archival data source.

FIG. 5B is a flowchart describing one embodiment of a process forgenerating one or more virtual machines for consolidating expiredsnapshots.

FIG. 5C is a flowchart describing one embodiment of a process forconsolidating expired snapshots.

FIG. 5D is a flowchart describing one embodiment of a process forgenerating one or more full image snapshots to enable deletion ofexpired snapshots.

FIGS. 6A-6J depict various embodiments of different versions of avirtual machine and their corresponding electronic files stored using afirst storage domain (Domain A) and a second storage domain (Domain B).

FIG. 7A is a flowchart describing one embodiment of a process fortransferring snapshots of a virtual machine from a first storage domainto a second storage domain.

FIG. 7B is a flowchart describing another embodiment of a process fortransferring snapshots of a virtual machine from a first storage domainto a second storage domain.

DETAILED DESCRIPTION

Technology is described for reclaiming disk space by consolidatingand/or deleting expired snapshots stored within a data storage domain.The data storage domain may correspond with a cluster of data storagenodes or an archival data source. The expired snapshots may comprisesnapshots of a virtual machine, an application, a database, or anelectronic file that are no longer required to be stored (e.g., therequirements of an SLA policy may no longer require that the snapshotsbe stored or recoverable). The snapshots may be stored or archived usingan archival data store (e.g., an NFS datastore), cloud storage, objectstorage (e.g., data storage that manages or stores data as objects), orblock storage. The archival data source may comprise an archival datastore, a hardware data storage device, a storage area network storagedevice, a networked-attached storage device, or a cloud-based datastorage system. The stored snapshots may include a full image snapshotand one or more incremental files that derive from the full imagesnapshot. Disk space within the data storage domain or on the archivaldata source may be reclaimed by either consolidating or mergingconsecutive expired snapshots or by deleting expired snapshots. In somecases, rather than archiving an incremental file corresponding with aparticular snapshot, a full image of the particular snapshot may begenerated and stored within the archival data source. The generation ofthe full image may allow a chain of dependencies supporting the expiredsnapshots to be broken and for the expired snapshots to be deleted orconsolidated on the archival data source. The generation of full imagesmay be performed periodically in order to reduce the size of thedependency chains for the archived snapshots. One benefit of reclaimingdisk space by consolidating and/or deleting expired snapshots is thatavailable disk space may be increased and the costs associated withstoring the archived data may be reduced.

In one embodiment, a full image of a particular snapshot may begenerated using compute resources accessible by an archival data source(e.g., compute on cloud capability may enable the instantiation of avirtual machine to generate the full image in the cloud). The particularsnapshot stored within the archival data source may be identified basedon a maximum dependency size for chains within the archival data source.In one example, the maximum dependency size for a chain may comprise amaximum of ten dependencies requiring that the maximum number ofincrementals between any two full image snapshots is not more than nineincremental snapshots. The particular snapshot may be identified as themost recently uploaded snapshot to the archival data source or as thenewest version of a virtual machine that is stored within the archivaldata store. In some cases, the determination of whether to generate thefull image for the particular snapshot using compute resources (e.g., avirtual machine) or to keep an incremental snapshot may depend on theamount of available disk space, the total number of expired snapshots,and/or the combined data size for the expired snapshots. In one example,the full image for the particular snapshot may be generated in responseto detecting that the total number of expired snapshots is greater thana threshold number of snapshots, that the amount of available disk spaceon the archival data source is below a threshold amount of disk space,and/or that the combined data size of the expired snapshots is greaterthan a threshold data size (e.g., more than 200GB of disk space may bereclaimed on the archival data source if the full image for theparticular snapshot is generated).

In another embodiment, rather than transferring an incremental filecorresponding with a particular snapshot to an archival data source, afull image of the particular snapshot may be generated and uploaded tothe archival data source (e.g., a local storage appliance may generatethe full image and then transfer the full image to cloud storage). Inone example, a full image snapshot may be generated and uploaded to thearchival data source instead of an incremental file in response todetecting that a time difference between the current snapshot to beuploaded and the last uploaded full image snapshot is greater than athreshold period of time (e.g., it has been more than 30 days since thelast full image snapshot was uploaded). In another example, the fullimage snapshot may be generated and uploaded to the archival data sourcein response to detecting that a number of archived snapshots between thecurrent snapshot to be uploaded and the last uploaded full imagesnapshot is greater than a threshold number of snapshots (e.g., therehave been more than 200 snapshots archived since the last full imagesnapshot was uploaded). In another example, the full image snapshot maybe generated and uploaded to the archival data source in response todetecting that an accumulated data size of the archived snapshotsuploaded since the last full image snapshot was uploaded is greater thana threshold data size (e.g., is greater than 1 TB or greater than thedata size of the last uploaded full image snapshot). In another example,the full image snapshot may be generated and uploaded to the archivaldata source in response to detecting that a combined data size of priorincremental snapshots uploaded to the archival data source since thelast uploaded full image snapshot is greater than a threshold data size(e.g., is greater than 500 GB) and/or more than a threshold time periodhas passed since the last full image snapshot was uploaded to thearchival data source (e.g., more than 15 days have passed since the lastfull image snapshot was uploaded). In another example, the full imagesnapshot may be generated and uploaded to the archival data source inresponse to detecting that a change rate computed as the summation ofthe physical disk sizes of the incremental files uploaded to thearchival data source since the last full image snapshot was uploadeddivided by the physical disk size of the last full image snapshot isgreater than a threshold percentage (e.g., is greater than 100% of thesize of the last uploaded full image snapshot).

Technology is also described for managing the transfer of snapshot databetween two different data storage domains. In some cases, snapshot datastored using a local data storage cluster may be transferred tocloud-based data storage or to a remote data storage cluster in order tostore archived snapshot data or to allow non-archived snapshot data tobe used by the cloud-based data storage or the remote data storagecluster. In one example, the most recent snapshot of a virtual machine(e.g., the last captured snapshot for the virtual machine) that has notyet been archived may be prematurely uploaded to cloud-based datastorage or to the remote data storage cluster in order to facilitatetesting or development using the most recent snapshot of the virtualmachine. In this case, the most recent snapshot of the virtual machinemay be transferred to cloud-based data storage or to the remote datastorage cluster by transferring an out-of-order incremental file for themost recent version of the virtual machine.

An out-of-order incremental file may correspond with data differencesbetween the most recent version of the virtual machine stored using alocal data storage cluster (e.g., corresponding with the last capturedsnapshot of the virtual machine stored within a first data storagedomain) and a second snapshot of the virtual machine stored using aremote data storage cluster (e.g., corresponding with the last uploadedsnapshot of the virtual machine transferred to a second data storagedomain). The most recent snapshot of the virtual machine may beassociated with a first point in time version of the virtual machine andthe second snapshot of the virtual machine may be associated with asecond point in time version of the virtual machine that does notdirectly precede the first point in time version of the virtual machine.In one example, the most recent snapshot of the virtual machine maycorrespond with a tenth version of the virtual machine and the secondsnapshot of the virtual machine may correspond with a third version ofthe virtual machine. In this case, the out-of-order incremental file maycomprise data differences between the tenth version of the virtualmachine and the third version of the virtual machine. In contrast, anin-order incremental file may comprise data differences between thetenth version of the virtual machine and the ninth version of thevirtual machine (i.e., the version of the virtual machine that directlyprecedes the tenth version of the virtual machine).

After the out-of-order incremental file has been transferred to thesecond data storage domain, a full image for the most recent snapshot ofthe virtual machine may be generated using a chain of snapshots that arealready stored within the second data storage domain. The full image forthe most recent snapshot of the virtual machine may be used to generatea virtual machine instance. One benefit of transferring out-of-orderincremental files is that by leveraging the chain of snapshots that havealready been archived or otherwise transferred to cloud-based datastorage or to the remote data storage cluster, the most recent versionof a virtual machine that has not yet been archived may be madeavailable to computing resources within the cloud-based data storage orthe remote data storage cluster with reduced upload time and reducednetwork congestion. Another benefit of transferring out-of-orderincremental files is that future data transfers from the first datastorage domain to the second data storage domain may leverage theadditional out-of-order incremental files that were previouslytransferred to the second storage domain to reduce the data size offuture incremental file transfers and to reduce the disk space requiredto store the archived snapshots of the virtual machine in the seconddata storage domain.

An integrated data management and storage system may be configured tomanage the automated storage, backup, deduplication, replication,recovery, and archival of data within and across physical and virtualcomputing environments. The integrated data management and storagesystem may provide a unified primary and secondary storage system withbuilt-in data management that may be used as both a backup storagesystem and a “live” primary storage system for primary workloads. Insome cases, the integrated data management and storage system may managethe extraction and storage of historical snapshots associated withdifferent point in time versions of virtual machines and/or realmachines (e.g., a hardware server, a laptop, a tablet computer, asmartphone, or a mobile computing device) and provide near instantaneousrecovery of a backed-up version of a virtual machine, a real machine, orone or more files residing on the virtual machine or the real machine.The integrated data management and storage system may allow backed-upversions of real or virtual machines to be directly mounted or madeaccessible to primary workloads in order to enable the nearinstantaneous recovery of the backed-up versions and allow secondaryworkloads (e.g., workloads for experimental or analytics purposes) todirectly use the integrated data management and storage system as aprimary storage target to read or modify past versions of data.

The integrated data management and storage system may include adistributed cluster of storage nodes that presents itself as a unifiedstorage system even though numerous storage nodes may be connectedtogether and the number of connected storage nodes may change over timeas storage nodes are added to or removed from the cluster. Theintegrated data management and storage system may utilize a scale-outnode based architecture in which a plurality of data storage appliancescomprising one or more nodes are in communication with each other viaone or more networks. Each storage node may include two or moredifferent types of storage devices and control circuitry configured tostore, deduplicate, compress, and/or encrypt data stored using the twoor more different types of storage devices. In one example, a storagenode may include two solid-state drives (SSDs), three hard disk drives(HDDs), and one or more processors configured to concurrently read datafrom and/or write data to the storage devices. The integrated datamanagement and storage system may replicate and distribute versioneddata, metadata, and task execution across the distributed cluster toincrease tolerance to node and disk failures (e.g., snapshots of avirtual machine may be triply mirrored across the cluster). Datamanagement tasks may be assigned and executed across the distributedcluster in a fault tolerant manner based on the location of data withinthe cluster (e.g., assigning tasks to nodes that store data related tothe task) and node resource availability (e.g., assigning tasks to nodeswith sufficient compute or memory capacity for the task).

The integrated data management and storage system may apply a databackup and archiving schedule to backed-up real and virtual machines toenforce various backup service level agreements (SLAs), recovery pointobjectives (RPOs), recovery time objectives (RTOs), data retentionrequirements, and other data backup, replication, and archival policiesacross the entire data lifecycle. For example, the data backup andarchiving schedule may require that snapshots of a virtual machine arecaptured and stored every four hours for the past week, every day forthe past six months, and every week for the past five years.

As virtualization technologies are adopted into information technology(IT) infrastructures, there is a growing need for recovery mechanisms tosupport mission critical application deployment within a virtualizedinfrastructure. However, a virtualized infrastructure may present a newset of challenges to the traditional methods of data management due tothe higher workload consolidation and the need for instant, granularrecovery. The benefits of using an integrated data management andstorage system include the ability to reduce the amount of data storagerequired to backup real and virtual machines, the ability to reduce theamount of data storage required to support secondary or non-productionworkloads, the ability to provide a non-passive storage target in whichbackup data may be directly accessed and modified, and the ability toquickly restore earlier versions of virtual machines and files storedlocally or in the cloud.

FIG. 1A depicts one embodiment of a networked computing environment 100in which the disclosed technology may be practiced. As depicted, thenetworked computing environment 100 includes a data center 150, astorage appliance 140, and a computing device 154 in communication witheach other via one or more networks 180. The networked computingenvironment 100 may include a plurality of computing devicesinterconnected through one or more networks 180. The one or morenetworks 180 may allow computing devices and/or storage devices toconnect to and communicate with other computing devices and/or otherstorage devices. In some cases, the networked computing environment mayinclude other computing devices and/or other storage devices not shown.The other computing devices may include, for example, a mobile computingdevice, a non-mobile computing device, a server, a workstation, a laptopcomputer, a tablet computer, a desktop computer, or an informationprocessing system. The other storage devices may include, for example, astorage area network storage device, a networked-attached storagedevice, a hard disk drive, a solid-state drive, or a data storagesystem. The one or more networks 180 may include a cellular network, amobile network, a wireless network, a wired network, a secure networksuch as an enterprise private network, an unsecure network such as awireless open network, a local area network (LAN), a wide area network(WAN), and the Internet.

The data center 150 may include one or more servers, such as server 160,in communication with one or more storage devices, such as storagedevice 156. The one or more servers may also be in communication withone or more storage appliances, such as storage appliance 170. Theserver 160, storage device 156, and storage appliance 170 may be incommunication with each other via a networking fabric connecting serversand data storage units within the data center to each other. The server160 may comprise a production hardware server. The storage appliance 170may include a data management system for backing up virtual machines,real machines, virtual disks, real disks, and/or electronic files withinthe data center 150. The server 160 may be used to create and manage oneor more virtual machines associated with a virtualized infrastructure.The one or more virtual machines may run various applications, such as adatabase application or a web server. The storage device 156 may includeone or more hardware storage devices for storing data, such as a harddisk drive (HDD), a magnetic tape drive, a solid-state drive (SSD), astorage area network (SAN) storage device, or a networked-attachedstorage (NAS) device. In some cases, a data center, such as data center150, may include thousands of servers and/or data storage devices incommunication with each other. The data storage devices may comprise atiered data storage infrastructure (or a portion of a tiered datastorage infrastructure). The tiered data storage infrastructure mayallow for the movement of data across different tiers of a data storageinfrastructure between higher-cost, higher-performance storage devices(e.g., solid-state drives and hard disk drives) and relativelylower-cost, lower-performance storage devices (e.g., magnetic tapedrives).

A server, such as server 160, may allow a client to download informationor files (e.g., executable, text, application, audio, image, or videofiles) from the server or to perform a search query related toparticular information stored on the server. In some cases, a server mayact as an application server or a file server. In general, a server mayrefer to a hardware device that acts as the host in a client-serverrelationship or a software process that shares a resource with orperforms work for one or more clients. One embodiment of server 160includes a network interface 165, processor 166, memory 167, disk 168,and virtualization manager 169 all in communication with each other.Network interface 165 allows server 160 to connect to one or morenetworks 180. Network interface 165 may include a wireless networkinterface and/or a wired network interface. Processor 166 allows server160 to execute computer readable instructions stored in memory 167 inorder to perform processes described herein. Processor 166 may includeone or more processing units, such as one or more CPUs and/or one ormore GPUs. Memory 167 may comprise one or more types of memory (e.g.,RAM, SRAM, DRAM, ROM, EEPROM, Flash, etc.). Disk 168 may include a harddisk drive and/or a solid-state drive. Memory 167 and disk 168 maycomprise hardware storage devices.

The virtualization manager 169 may manage a virtualized infrastructureand perform management operations associated with the virtualizedinfrastructure. For example, the virtualization manager 169 may managethe provisioning of virtual machines running within the virtualizedinfrastructure and provide an interface to computing devices interactingwith the virtualized infrastructure. The virtualization manager 169 mayalso perform various virtual machine related tasks, such as cloningvirtual machines, creating new virtual machines, monitoring the state ofvirtual machines, moving virtual machines between physical hosts forload balancing purposes, and facilitating backups of virtual machines.

One embodiment of storage appliance 170 includes a network interface175, processor 176, memory 177, and disk 178 all in communication witheach other. Network interface 175 allows storage appliance 170 toconnect to one or more networks 180. Network interface 175 may include awireless network interface and/or a wired network interface. Processor176 allows storage appliance 170 to execute computer readableinstructions stored in memory 177 in order to perform processesdescribed herein. Processor 176 may include one or more processingunits, such as one or more CPUs and/or one or more GPUs. Memory 177 maycomprise one or more types of memory (e.g., RAM, SRAM, DRAM, ROM,EEPROM, NOR Flash, NAND Flash, etc.). Disk 178 may include a hard diskdrive and/or a solid-state drive. Memory 177 and disk 178 may comprisehardware storage devices.

In one embodiment, the storage appliance 170 may include four machines.Each of the four machines may include a multi-core CPU, 64 GB of RAM, a400 GB SSD, three 4 TB HDDs, and a network interface controller. In thiscase, the four machines may be in communication with the one or morenetworks 180 via the four network interface controllers. The fourmachines may comprise four nodes of a server cluster. The server clustermay comprise a set of physical machines that are connected together viaa network. The server cluster may be used for storing data associatedwith a plurality of virtual machines, such as backup data associatedwith different point in time versions of one or more virtual machines.

In another embodiment, the storage appliance 170 may comprise a virtualappliance that comprises four virtual machines. Each of the virtualmachines in the virtual appliance may have 64 GB of virtual memory, a 12TB virtual disk, and a virtual network interface controller. In thiscase, the four virtual machines may be in communication with the one ormore networks 180 via the four virtual network interface controllers.The four virtual machines may comprise four nodes of a virtual cluster.

The networked computing environment 100 may provide a cloud computingenvironment for one or more computing devices. In one embodiment, thenetworked computing environment 100 may include a virtualizedinfrastructure that provides software, data processing, and/or datastorage services to end users accessing the services via the networkedcomputing environment. In one example, networked computing environment100 may provide cloud-based work productivity or business relatedapplications to a computing device, such as computing device 154. Thecomputing device 154 may comprise a mobile computing device or a tabletcomputer. The storage appliance 140 may comprise a cloud-based datamanagement system for backing up virtual machines and/or files within avirtualized infrastructure, such as virtual machines running on server160 or files stored on server 160.

In some embodiments, the storage appliance 170 may manage the extractionand storage of virtual machine snapshots associated with different pointin time versions of one or more virtual machines running within the datacenter 150. A snapshot of a virtual machine may correspond with a stateof the virtual machine at a particular point in time. In some cases, thesnapshot may capture the state of various virtual machine settings andthe state of one or more virtual disks for the virtual machine. Inresponse to a restore command from the server 160, the storage appliance170 may restore a point in time version of a virtual machine or restorepoint in time versions of one or more files located on the virtualmachine and transmit the restored data to the server 160. In response toa mount command from the server 160, the storage appliance 170 may allowa point in time version of a virtual machine to be mounted and allow theserver 160 to read and/or modify data associated with the point in timeversion of the virtual machine. To improve storage density, the storageappliance 170 may deduplicate and compress data associated withdifferent versions of a virtual machine and/or deduplicate and compressdata associated with different virtual machines. To improve systemperformance, the storage appliance 170 may first store virtual machinesnapshots received from a virtualized environment in a cache, such as aflash-based cache. The cache may also store popular data or frequentlyaccessed data (e.g., based on a history of virtual machinerestorations), incremental files associated with commonly restoredvirtual machine versions, and current day incremental files orincremental files corresponding with snapshots captured within the past24 hours.

An incremental file may comprise a forward incremental file or a reverseincremental file. A forward incremental file may include a set of datarepresenting changes that have occurred since an earlier point in timesnapshot of a virtual machine. To generate a snapshot of the virtualmachine corresponding with a forward incremental file, the forwardincremental file may be combined with an earlier point in time snapshotof the virtual machine (e.g., the forward incremental file may becombined with the last full image of the virtual machine that wascaptured before the forward incremental was captured and any otherforward incremental files that were captured subsequent to the last fullimage and prior to the forward incremental file). A reverse incrementalfile may include a set of data representing changes from a later pointin time snapshot of a virtual machine. To generate a snapshot of thevirtual machine corresponding with a reverse incremental file, thereverse incremental file may be combined with a later point in timesnapshot of the virtual machine (e.g., the reverse incremental file maybe combined with the most recent snapshot of the virtual machine and anyother reverse incremental files that were captured prior to the mostrecent snapshot and subsequent to the reverse incremental file).

The storage appliance 170 may provide a user interface (e.g., aweb-based interface or a graphical user interface) that displays virtualmachine information, such as identifications of the virtual machinesprotected and the historical versions or time machine views for each ofthe virtual machines protected, and allows an end user to search,select, and control virtual machines managed by the storage appliance. Atime machine view of a virtual machine may include snapshots of thevirtual machine over a plurality of points in time. Each snapshot maycomprise the state of the virtual machine at a particular point in time.Each snapshot may correspond with a different version of the virtualmachine (e.g., Version 1 of a virtual machine may correspond with thestate of the virtual machine at a first point in time and Version 2 ofthe virtual machine may correspond with the state of the virtual machineat a second point in time subsequent to the first point in time).

FIG. 1B depicts one embodiment of server 160 in FIG. 1A. The server 160may comprise one server out of a plurality of servers that are networkedtogether within a data center. In one example, the plurality of serversmay be positioned within one or more server racks within the datacenter. As depicted, the server 160 includes hardware-level componentsand software-level components. The hardware-level components include oneor more processors 182, one or more memory 184, and one or more disks185. The software-level components include a hypervisor 186, avirtualized infrastructure manager 199, and one or more virtualmachines, such as virtual machine 198. The hypervisor 186 may comprise anative hypervisor or a hosted hypervisor. The hypervisor 186 may providea virtual operating platform for running one or more virtual machines,such as virtual machine 198. Virtual machine 198 includes a plurality ofvirtual hardware devices including a virtual processor 192, a virtualmemory 194, and a virtual disk 195. The virtual disk 195 may comprise afile stored within the one or more disks 185. In one example, a virtualmachine may include a plurality of virtual disks, with each virtual diskof the plurality of virtual disks associated with a different filestored on the one or more disks 185. Virtual machine 198 may include aguest operating system 196 that runs one or more applications, such asapplication 197. The virtualized infrastructure manager 199, which maycorrespond with the virtualization manager 169 in FIG. 1A, may run on avirtual machine or natively on the server 160. The virtualizedinfrastructure manager 199 may provide a centralized platform formanaging a virtualized infrastructure that includes a plurality ofvirtual machines.

In one embodiment, the server 160 may use the virtualized infrastructuremanager 199 to facilitate backups for a plurality of virtual machines(e.g., eight different virtual machines) running on the server 160. Eachvirtual machine running on the server 160 may run its own guestoperating system and its own set of applications. Each virtual machinerunning on the server 160 may store its own set of files using one ormore virtual disks associated with the virtual machine (e.g., eachvirtual machine may include two virtual disks that are used for storingdata associated with the virtual machine).

In one embodiment, a data management application running on a storageappliance, such as storage appliance 140 in FIG. 1A or storage appliance170 in FIG. 1A, may request a snapshot of a virtual machine running onserver 160. The snapshot of the virtual machine may be stored as one ormore files, with each file associated with a virtual disk of the virtualmachine. A snapshot of a virtual machine may correspond with a state ofthe virtual machine at a particular point in time. The particular pointin time may be associated with a time stamp. In one example, a firstsnapshot of a virtual machine may correspond with a first state of thevirtual machine (including the state of applications and files stored onthe virtual machine) at a first point in time (e.g., 6:30 p.m. on Jun.29, 2017) and a second snapshot of the virtual machine may correspondwith a second state of the virtual machine at a second point in timesubsequent to the first point in time (e.g., 6:30 p.m. on Jun. 30,2017).

In response to a request for a snapshot of a virtual machine at aparticular point in time, the virtualized infrastructure manager 199 mayset the virtual machine into a frozen state or store a copy of thevirtual machine at the particular point in time. The virtualizedinfrastructure manager 199 may then transfer data associated with thevirtual machine (e.g., an image of the virtual machine or a portion ofthe image of the virtual machine) to the storage appliance. The dataassociated with the virtual machine may include a set of files includinga virtual disk file storing contents of a virtual disk of the virtualmachine at the particular point in time and a virtual machineconfiguration file storing configuration settings for the virtualmachine at the particular point in time. The contents of the virtualdisk file may include the operating system used by the virtual machine,local applications stored on the virtual disk, and user files (e.g.,images and word processing documents). In some cases, the virtualizedinfrastructure manager 199 may transfer a full image of the virtualmachine to the storage appliance or a plurality of data blockscorresponding with the full image (e.g., to enable a full image-levelbackup of the virtual machine to be stored on the storage appliance). Inother cases, the virtualized infrastructure manager 199 may transfer aportion of an image of the virtual machine associated with data that haschanged since an earlier point in time prior to the particular point intime or since a last snapshot of the virtual machine was taken. In oneexample, the virtualized infrastructure manager 199 may transfer onlydata associated with changed blocks stored on a virtual disk of thevirtual machine that have changed since the last snapshot of the virtualmachine was taken. In one embodiment, the data management applicationmay specify a first point in time and a second point in time and thevirtualized infrastructure manager 199 may output one or more changeddata blocks associated with the virtual machine that have been modifiedbetween the first point in time and the second point in time.

FIG. 1C depicts one embodiment of a storage appliance, such as storageappliance 170 in FIG. 1A. The storage appliance may include a pluralityof physical machines that may be grouped together and presented as asingle computing system. Each physical machine of the plurality ofphysical machines may comprise a node in a cluster (e.g., a failovercluster). As depicted, the storage appliance 170 includes hardware-levelcomponents and software-level components. The hardware-level componentsinclude one or more physical machines, such as physical machine 120 andphysical machine 130. The physical machine 120 includes a networkinterface 121, processor 122, memory 123, and disk 124 all incommunication with each other. Processor 122 allows physical machine 120to execute computer readable instructions stored in memory 123 toperform processes described herein. Disk 124 may include a hard diskdrive and/or a solid-state drive. The physical machine 130 includes anetwork interface 131, processor 132, memory 133, and disk 134 all incommunication with each other. Processor 132 allows physical machine 130to execute computer readable instructions stored in memory 133 toperform processes described herein. Disk 134 may include a hard diskdrive and/or a solid-state drive. In some cases, disk 134 may include aflash-based SSD or a hybrid HDD/SSD drive. In one embodiment, thestorage appliance 170 may include a plurality of physical machinesarranged in a cluster (e.g., eight machines in a cluster). Each of theplurality of physical machines may include a plurality of multi-coreCPUs, 128 GB of RAM, a 500 GB SSD, four 4 TB HDDs, and a networkinterface controller.

As depicted in FIG. 1C, the software-level components of the storageappliance 170 may include data management system 102, a virtualizationinterface 104, a distributed job scheduler 108, a distributed metadatastore 110, a distributed file system 112, and one or more virtualmachine search indexes, such as virtual machine search index 106. In oneembodiment, the software-level components of the storage appliance 170may be run using a dedicated hardware-based appliance. In anotherembodiment, the software-level components of the storage appliance 170may be run from the cloud (e.g., the software-level components may beinstalled on a cloud service provider).

In some cases, the data storage across a plurality of nodes in a cluster(e.g., the data storage available from the one or more physicalmachines) may be aggregated and made available over a single file systemnamespace (e.g., /snapshots/). A directory for each virtual machineprotected using the storage appliance 170 may be created (e.g., thedirectory for Virtual Machine A may be /snapshots/VM_A). Snapshots andother data associated with a virtual machine may reside within thedirectory for the virtual machine. In one example, snapshots of avirtual machine may be stored in subdirectories of the directory (e.g.,a first snapshot of Virtual Machine A may reside in /snapshots/VM_A/s1/and a second snapshot of Virtual Machine A may reside in/snapshots/VM_A/s2/).

The distributed file system 112 may present itself as a single filesystem, in which as new physical machines or nodes are added to thestorage appliance 170, the cluster may automatically discover theadditional nodes and automatically increase the available capacity ofthe file system for storing files and other data. Each file stored inthe distributed file system 112 may be partitioned into one or morechunks. Each of the one or more chunks may be stored within thedistributed file system 112 as a separate file. The files stored withinthe distributed file system 112 may be replicated or mirrored over aplurality of physical machines, thereby creating a load-balanced andfault tolerant distributed file system. In one example, storageappliance 170 may include ten physical machines arranged as a failovercluster and a first file corresponding with a full-image snapshot of avirtual machine (e.g., /snapshots/VM_A/s1/s1.full) may be replicated andstored on three of the ten machines. In some cases, the data chunksassociated with a file stored in the distributed file system 112 mayinclude replicated data (e.g., due to n-way mirroring) or parity data(e.g., due to erasure coding). When a disk storing one of the datachunks fails, then the distributed file system may regenerate the lostdata and store the lost data using a new disk.

In one embodiment, the distributed file system 112 may be used to storea set of versioned files corresponding with a virtual machine. The setof versioned files may include a first file comprising a full image ofthe virtual machine at a first point in time and a second filecomprising an incremental file relative to the full image. The set ofversioned files may correspond with a snapshot chain for the virtualmachine. The distributed file system 112 may determine a first set ofdata chunks that includes redundant information for the first file(e.g., via application of erasure code techniques) and store the firstset of data chunks across a plurality of nodes within a cluster. Theplacement of the first set of data chunks may be determined based on thelocations of other data related to the first set of data chunks (e.g.,the locations of other chunks corresponding with the second file orother files within the snapshot chain for the virtual machine). In someembodiments, the distributed file system 112 may also co-locate datachunks or replicas of virtual machines discovered to be similar to eachother in order to allow for cross virtual machine deduplication. In thiscase, the placement of the first set of data chunks may be determinedbased on the locations of other data corresponding with a differentvirtual machine that has been determined to be sufficiently similar tothe virtual machine.

The distributed metadata store 110 may comprise a distributed databasemanagement system that provides high availability without a single pointof failure. The distributed metadata store 110 may act as a quick-accessdatabase for various components in the software stack of the storageappliance 170 and may store metadata corresponding with stored snapshotsusing a SSD or a Flash-based storage device. In one embodiment, thedistributed metadata store 110 may comprise a database, such as adistributed document oriented database. The distributed metadata store110 may be used as a distributed key value storage system. In oneexample, the distributed metadata store 110 may comprise a distributedNoSQL key value store database. In some cases, the distributed metadatastore 110 may include a partitioned row store, in which rows areorganized into tables or other collections of related data held within astructured format within the key value store database. A table (or a setof tables) may be used to store metadata information associated with oneor more files stored within the distributed file system 112. Themetadata information may include the name of a file, a size of the file,file permissions associated with the file, when the file was lastmodified, and file mapping information associated with an identificationof the location of the file stored within a cluster of physicalmachines. In one embodiment, a new file corresponding with a snapshot ofa virtual machine may be stored within the distributed file system 112and metadata associated with the new file may be stored within thedistributed metadata store 110. The distributed metadata store 110 mayalso be used to store a backup schedule for the virtual machine and alist of snapshots for the virtual machine that are stored using thestorage appliance 170.

In some cases, the distributed metadata store 110 may be used to manageone or more versions of a virtual machine. Each version of the virtualmachine may correspond with a full image snapshot of the virtual machinestored within the distributed file system 112 or an incremental snapshotof the virtual machine (e.g., a forward incremental or reverseincremental) stored within the distributed file system 112. In oneembodiment, the one or more versions of the virtual machine maycorrespond with a plurality of files. The plurality of files may includea single full image snapshot of the virtual machine and one or moreincrementals derived from the single full image snapshot. The singlefull image snapshot of the virtual machine may be stored using a firststorage device of a first type (e.g., a HDD) and the one or moreincrementals derived from the single full image snapshot may be storedusing a second storage device of a second type (e.g., an SSD). In thiscase, only a single full image needs to be stored and each version ofthe virtual machine may be generated from the single full image or thesingle full image combined with a subset of the one or moreincrementals. Furthermore, each version of the virtual machine may begenerated by performing a sequential read from the first storage device(e.g., reading a single file from a HDD) to acquire the full image and,in parallel, performing one or more reads from the second storage device(e.g., performing fast random reads from an SSD) to acquire the one ormore incrementals. In some cases, a first version of a virtual machinecorresponding with a first snapshot of the virtual machine at a firstpoint in time may be generated by concurrently reading a full image forthe virtual machine corresponding with a state of the virtual machineprior to the first point in time from the first storage device whilereading one or more incrementals from the second storage devicedifferent from the first storage device (e.g., reading the full imagefrom a HDD at the same time as reading 64 incrementals from an SSD).

The distributed job scheduler 108 may comprise a distributed faulttolerant job scheduler, in which jobs affected by node failures arerecovered and rescheduled to be run on available nodes. In oneembodiment, the distributed job scheduler 108 may be fully decentralizedand implemented without the existence of a master node. The distributedjob scheduler 108 may run job scheduling processes on each node in acluster or on a plurality of nodes in the cluster and each node mayindependently determine which tasks to execute. The distributed jobscheduler 108 may be used for scheduling backup jobs that acquire andstore virtual machine snapshots for one or more virtual machines overtime. The distributed job scheduler 108 may follow a backup schedule tobackup an entire image of a virtual machine at a particular point intime or one or more virtual disks associated with the virtual machine atthe particular point in time.

The job scheduling processes running on at least a plurality of nodes ina cluster (e.g., on each available node in the cluster) may manage thescheduling and execution of a plurality of jobs. The job schedulingprocesses may include run processes for running jobs, cleanup processesfor cleaning up failed tasks, and rollback processes for rolling-back orundoing any actions or tasks performed by failed jobs. In oneembodiment, the job scheduling processes may detect that a particulartask for a particular job has failed and in response may perform acleanup process to clean up or remove the effects of the particular taskand then perform a rollback process that processes one or more completedtasks for the particular job in reverse order to undo the effects of theone or more completed tasks. Once the particular job with the failedtask has been undone, the job scheduling processes may restart theparticular job on an available node in the cluster.

The virtualization interface 104 may provide an interface forcommunicating with a virtualized infrastructure manager managing avirtualization infrastructure, such as virtualized infrastructuremanager 199 in FIG. 1B, and requesting data associated with virtualmachine snapshots from the virtualization infrastructure. Thevirtualization interface 104 may communicate with the virtualizedinfrastructure manager using an API for accessing the virtualizedinfrastructure manager (e.g., to communicate a request for a snapshot ofa virtual machine).

The virtual machine search index 106 may include a list of files thathave been stored using a virtual machine and a version history for eachof the files in the list. Each version of a file may be mapped to theearliest point in time snapshot of the virtual machine that includes theversion of the file or to a snapshot of the virtual machine thatincludes the version of the file (e.g., the latest point in timesnapshot of the virtual machine that includes the version of the file).In one example, the virtual machine search index 106 may be used toidentify a version of the virtual machine that includes a particularversion of a file (e.g., a particular version of a database, aspreadsheet, or a word processing document). In some cases, each of thevirtual machines that are backed up or protected using storage appliance170 may have a corresponding virtual machine search index.

The data management system 102 may comprise an application running onthe storage appliance that manages the capturing, storing,deduplication, compression (e.g., using a lossless data compressionalgorithm such as LZ4 or LZ77), and encryption (e.g., using a symmetrickey algorithm such as Triple DES or AES-256) of data for the storageappliance 170. In one example, the data management system 102 maycomprise a highest level layer in an integrated software stack runningon the storage appliance. The integrated software stack may include thedata management system 102, the virtualization interface 104, thedistributed job scheduler 108, the distributed metadata store 110, andthe distributed file system 112. In some cases, the integrated softwarestack may run on other computing devices, such as a server or computingdevice 154 in FIG. 1A. The data management system 102 may use thevirtualization interface 104, the distributed job scheduler 108, thedistributed metadata store 110, and the distributed file system 112 tomanage and store one or more snapshots of a virtual machine. Eachsnapshot of the virtual machine may correspond with a point in timeversion of the virtual machine. The data management system 102 maygenerate and manage a list of versions for the virtual machine. Eachversion of the virtual machine may map to or reference one or morechunks and/or one or more files stored within the distributed filesystem 112. Combined together, the one or more chunks and/or the one ormore files stored within the distributed file system 112 may comprise afull image of the version of the virtual machine.

In some embodiments, a plurality of versions of a virtual machine may bestored as a base file associated with a complete image of the virtualmachine at a particular point in time and one or more incremental filesassociated with forward and/or reverse incremental changes derived fromthe base file. The data management system 102 may patch together thebase file and the one or more incremental files in order to generate aparticular version of the plurality of versions by adding and/orsubtracting data associated with the one or more incremental files fromthe base file or intermediary files derived from the base file. In someembodiments, each version of the plurality of versions of a virtualmachine may correspond with a merged file. A merged file may includepointers or references to one or more files and/or one or more chunksassociated with a particular version of a virtual machine. In oneexample, a merged file may include a first pointer or symbolic link to abase file and a second pointer or symbolic link to an incremental fileassociated with the particular version of the virtual machine. In someembodiments, the one or more incremental files may correspond withforward incrementals (e.g., positive deltas), reverse incrementals(e.g., negative deltas), or a combination of both forward incrementalsand reverse incrementals.

FIG. 1D depicts one embodiment of a portion of an integrated datamanagement and storage system that includes a plurality of nodes incommunication with each other and one or more storage devices via one ormore networks 180. The plurality of nodes may be networked together andpresent themselves as a unified storage system. The plurality of nodesincludes node 141 and node 147. The one or more storage devices includestorage device 157 and storage device 158. Storage device 157 maycorrespond with a cloud-based storage (e.g., private or public cloudstorage). Storage device 158 may comprise a hard disk drive (HDD), amagnetic tape drive, a solid-state drive (SSD), a storage area network(SAN) storage device, or a networked-attached storage (NAS) device. Theintegrated data management and storage system may comprise a distributedcluster of storage appliances in which each of the storage appliancesincludes one or more nodes. In one embodiment, node 141 and node 147 maycomprise two nodes housed within a first storage appliance, such asstorage appliance 170 in FIG. 1C. In another embodiment, node 141 maycomprise a first node housed within a first storage appliance and node147 may comprise a second node housed within a second storage appliancedifferent from the first storage appliance. The first storage applianceand the second storage appliance may be located within a data center,such as data center 150 in FIG. 1A, or located within different datacenters.

As depicted, node 141 includes a network interface 142, a nodecontroller 143, and a first plurality of storage devices including HDDs144-145 and SSD 146. The first plurality of storage devices may comprisetwo or more different types of storage devices. The node controller 143may comprise one or more processors configured to store, deduplicate,compress, and/or encrypt data stored within the first plurality ofstorage devices. Node 147 includes a network interface 148, a nodecontroller 149, and a second plurality of storage devices including HDDs151-152 and SSD 153. The second plurality of storage devices maycomprise two or more different types of storage devices. The nodecontroller 149 may comprise one or more processors configured to store,deduplicate, compress, and/or encrypt data stored within the secondplurality of storage devices. In some cases, node 141 may correspondwith physical machine 120 in FIG. 1C and node 147 may correspond withphysical machine 130 in FIG. 1C.

FIGS. 2A-2Q depict various embodiments of sets of files and datastructures (e.g., implemented using merged files) associated withmanaging and storing snapshots of virtual machines.

FIG. 2A depicts one embodiment of a set of virtual machine snapshotsstored as a first set of files. The first set of files may be storedusing a distributed file system, such as distributed file system 112 inFIG. 1C. As depicted, the first set of files includes a set of reverseincrementals (R1-R4), a full image (Base), and a set of forwardincrementals (F1-F2). The set of virtual machine snapshots includesdifferent versions of a virtual machine (versions V1-V7 of VirtualMachine A) captured at different points in time (times T1-T7). In somecases, the file size of the reverse incremental R3 and the file size ofthe forward incremental F2 may both be less than the file size of thebase image corresponding with version V5 of Virtual Machine A. The baseimage corresponding with version V5 of Virtual Machine A may comprise afull image of Virtual Machine A at point in time T5. The base image mayinclude a virtual disk file for Virtual Machine A at point in time T5.The reverse incremental R3 corresponds with version V2 of VirtualMachine A and the forward incremental F2 corresponds with version V7 ofVirtual Machine A. The forward incremental F1 may be associated with thedata changes that occurred to Virtual Machine A between time T5 and timeT6. The forward incremental Fl may include one or more changed datablocks.

In some embodiments, each snapshot of the set of virtual machinesnapshots may be stored within a storage appliance, such as storageappliance 170 in FIG. 1A. In other embodiments, a first set of the setof virtual machine snapshots may be stored within a first storageappliance and a second set of the set of virtual machine snapshots maybe stored within a second storage appliance, such as storage appliance140 in FIG. 1A. In this case, a data management system may extend acrossboth the first storage appliance and the second storage appliance. Inone example, the first set of the set of virtual machine snapshots maybe stored within a local cluster repository (e.g., recent snapshots ofthe file may be located within a first data center) and the second setof the set of virtual machine snapshots may be stored within a remotecluster repository (e.g., older snapshots or archived snapshots of thefile may be located within a second data center) or a cloud repository.

FIG. 2B depicts one embodiment of a merged file for generating versionV7 of Virtual Machine A using the first set of files depicted in FIG.2A. The merged file includes a first pointer (pBase) that references thebase image Base (e.g., via the path /snapshots/VM_A/s5/s5.full), asecond pointer (pF1) that references the forward incremental Fl (e.g.,via the path /snapshots/VM_A/s6/s6.delta), and a third pointer (pF2)that references the forward incremental F2 (e.g., via the path/snapshots/VM_A/s7/s7.delta). In one embodiment, to generate the fullimage of version V7 of Virtual Machine A, the base image may beacquired, the data changes associated with forward incremental Fl may beapplied to (or patched to) the base image to generate an intermediateimage, and then the data changes associated with forward incremental F2may be applied to the intermediate image to generate the full image ofversion V7 of Virtual Machine A.

FIG. 2C depicts one embodiment of a merged file for generating versionV2 of Virtual Machine A using the first set of files depicted in FIG.2A. The merged file includes a first pointer (pBase) that references thebase image Base (e.g., via the path /snapshots/VM_A/s5/s5.full), asecond pointer (pR1) that references the reverse incremental R1 (e.g.,via the path /snapshots/VM_A/s4/s4.delta), a third pointer (pR2) thatreferences the reverse incremental R2 (e.g., via the path/snapshots/VM_A/s3/s3.delta), and a fourth pointer (pR3) that referencesthe reverse incremental R3 (e.g., via the path/snapshots/VM_A/s2/s2.delta). In one embodiment, to generate the fullimage of version V2 of Virtual Machine A, the base image may beacquired, the data changes associated with reverse incremental R1 may beapplied to the base image to generate a first intermediate image, thedata changes associated with reverse incremental R2 may be applied tothe first intermediate image to generate a second intermediate image,and then the data changes associated with reverse incremental R3 may beapplied to the second intermediate image to generate the full image ofversion V2 of Virtual Machine A.

FIG. 2D depicts one embodiment of a set of virtual machine snapshotsstored as a second set of files after a rebasing process has beenperformed using the first set of files in FIG. 2A. The second set offiles may be stored using a distributed file system, such as distributedfile system 112 in FIG. 1C. The rebasing process may generate new filesR12, R11, and Base2 associated with versions V5-V7 of Virtual Machine Ain order to move a full image closer to a more recent version of VirtualMachine A and to improve the reconstruction time for the more recentversions of Virtual Machine A. The data associated with the full imageBase in FIG. 2A may be equivalent to the new file R12 patched over R11and the full image Base2. Similarly, the data associated with the fullimage Base2 may be equivalent to the forward incremental F2 in FIG. 2Apatched over Fl and the full image Base in FIG. 2A.

The process of moving the full image snapshot for the set of virtualmachine snapshots to correspond with the most recent snapshot versionmay be performed in order to shorten or reduce the chain lengths for thenewest or most recent snapshots, which may comprise the snapshots ofVirtual Machine A that are the most likely to be accessed. In somecases, a rebasing operation (e.g., that moves the full image snapshotfor a set of virtual machine snapshots to correspond with the mostrecent snapshot version) or a reverse operation may be triggered when anumber of forward incremental files is greater than a threshold numberof forward incremental files for a snapshot chain (e.g., more than 200forward incremental files). In other cases, a rebasing operation or areverse operation may be triggered when the total disk size for theforward incremental files exceeds a threshold disk size (e.g., isgreater than 200 GB) or is greater than a threshold percentage (e.g., isgreater than 20%) of the base image for the snapshot chain.

In some cases, the rebasing process may be part of a periodic rebasingprocess that is applied at a rebasing frequency (e.g., every 24 hours)to each virtual machine of a plurality of protected virtual machines toreduce the number of forward incremental files that need to be patchedto a base image in order to restore the most recent version of a virtualmachine. Periodically reducing the number of forward incremental filesmay reduce the time to restore the most recent version of the virtualmachine as the number of forward incremental files that need to beapplied to a base image to generate the most recent version may belimited. In one example, if a rebasing process is applied to snapshotsof a virtual machine every 24 hours and snapshots of the virtual machineare acquired every four hours, then the number of forward incrementalfiles may be limited to at most five forward incremental files.

As depicted, the second set of files includes a set of reverseincrementals (R11-R12 and R1-R4) and a full image (Base2). The set ofvirtual machine snapshots includes the different versions of the virtualmachine (versions V1-V7 of Virtual Machine A) captured at the differentpoints in time (times T 1 -T7) depicted in FIG. 2A. In some cases, thefile size of the reverse incremental R2 may be substantially less thanthe file size of the base image Base2. The reverse incremental R2corresponds with version V2 of Virtual Machine A and the base imageBase2 corresponds with version V7 of Virtual Machine A. In this case,the most recent version of Virtual Machine A (i.e., the most recentrestore point for Virtual Machine A) comprises a full image. To generateearlier versions of Virtual Machine A, reverse incrementals may beapplied to (or patched to) the full image Base2. Subsequent versions ofVirtual Machine A may be stored as forward incrementals that depend fromthe full image Base2.

In one embodiment, a rebasing process may be applied to a first set offiles associated with a virtual machine in order to generate a secondset of files to replace the first set of files. The first set of filesmay include a first base image from which a first version of the virtualmachine may be derived and a first forward incremental file from which asecond version of the virtual machine may be derived. The second set offiles may include a second reverse incremental file from which the firstversion of the virtual machine may be derived and a second base imagefrom which the second version of the virtual machine may be derived.During the rebasing process, data integrity checking may be performed todetect and correct data errors in the files stored in a file system,such as distributed file system 112 in FIG. 1C, that are read togenerate the second set of files.

FIG. 2E depicts one embodiment of a merged file for generating versionV7 of Virtual Machine A using the second set of files depicted in FIG.2D. The merged file includes a first pointer (pBase2) that referencesthe base image Base2 (e.g., via the path /snapshots/VM_A/s7/s7.full). Inthis case, the full image of version V7 of Virtual Machine A may bedirectly acquired without patching forward incrementals or reverseincrementals to the base image Base2 corresponding with version V7 ofVirtual Machine A.

FIG. 2F depicts one embodiment of a merged file for generating versionV2 of Virtual Machine A using the second set of files depicted in FIG.2D. The merged file includes a first pointer (pBase2) that referencesthe base image Base2 (e.g., via the path /snapshots/VM_A/s7/s7.full), asecond pointer (pR11) that references the reverse incremental R11 (e.g.,via the path /snapshots/VM_A/s6/s6.delta), a third pointer (pR12) thatreferences the reverse incremental R12 (e.g., via the path/snapshots/VM_A/s5/s5.delta), a fourth pointer (pR1) that references thereverse incremental R1 (e.g., via the path /snapshots/VM_A/s4/s4.delta),a fifth pointer (pR2) that references the reverse incremental R2 (e.g.,via the path /snapshots/VM_A/s3/s3.delta), and a sixth pointer (pR3)that references the reverse incremental R3 (e.g., via the path/snapshots/VM_A/s2/s2.delta). In one embodiment, to generate the fullimage of version V2 of Virtual Machine A, the base image may beacquired, the data changes associated with reverse incremental R11 maybe applied to the base image to generate a first intermediate image, thedata changes associated with reverse incremental R12 may be applied tothe first intermediate image to generate a second intermediate image,the data changes associated with reverse incremental R1 may be appliedto the second intermediate image to generate a third intermediate image,the data changes associated with reverse incremental R2 may be appliedto the third intermediate image to generate a fourth intermediate image,and then the data changes associated with reverse incremental R3 may beapplied to the fourth intermediate image to generate the full image ofversion V2 of Virtual Machine A.

FIG. 2G depicts one embodiment of a set of files associated withmultiple virtual machine snapshots. The set of files may be stored usinga distributed file system, such as distributed file system 112 in FIG.1C. As depicted, the set of files includes a set of reverse incrementals(R1-R3), a full image (Base), and a set of forward incrementals (Fl-F2,F3, and F5-F6). In this case, a first version of Virtual Machine B maybe generated using a forward incremental F3 that derives from Version VXof Virtual Machine A and a second version of Virtual Machine C may begenerated using forward incrementals F5-F6 that are derived from VersionVZ of Virtual Machine A. In one example, Virtual Machine B may have beeninitially cloned from Version VX of Virtual Machine A and VirtualMachine C may have been initially cloned from Version VZ of VirtualMachine A.

In one embodiment, in response to a failure of a first virtual machinein a production environment (e.g., due to a failure of a physicalmachine running the first virtual machine), a most recent snapshot ofthe first virtual machine stored within a storage appliance, such asstorage appliance 170 in FIG. 1C, may be mounted and made available tothe production environment. In some cases, the storage appliance mayallow the most recent snapshot of the first virtual machine to bemounted by a computing device within the production environment, such asserver 160 in FIG. 1A. Once the most recent snapshot of the firstvirtual machine has been mounted, data stored within the most recentsnapshot of the first virtual machine may be read and/or modified andnew data may be written without the most recent snapshot of the firstvirtual machine being fully restored and transferred to the productionenvironment. In some cases, a server within the production environmentmay boot up a failed virtual machine directly from a storage appliance,such as storage appliance 170 in FIG. 1C, acting as an NFS datastore tominimize the recovery time to recover the failed virtual machine.

FIG. 2H depicts one embodiment of a merged file for generating versionV1 of Virtual Machine B using the set of files depicted in FIG. 2G. Themerged file includes a first pointer (pBase) that references the baseimage Base, a second pointer (pR1) that references the reverseincremental R1, a third pointer (pR2) that references the reverseincremental R2, and a fourth pointer (pF3) that references the forwardincremental F3. In one embodiment, to generate the full image of versionV1 of Virtual Machine B, the base image associated with Version VY ofVirtual Machine A may be acquired, the data changes associated withreverse incremental R1 may be applied to the base image to generate afirst intermediate image, the data changes associated with reverseincremental R2 may be applied to the first intermediate image togenerate a second intermediate image, and the data changes associatedwith forward incremental F3 may be applied to the second intermediateimage to generate the full image of version V1 of Virtual Machine B.

FIG. 2I depicts one embodiment of a merged file for generating versionV2 of Virtual Machine C using the set of files depicted in FIG. 2G. Themerged file includes a first pointer (pBase) that references the baseimage Base, a second pointer (pF1) that references the forwardincremental F1, a third pointer (pF5) that references the forwardincremental F5, and a fourth pointer (pF6) that references the forwardincremental F6. In one embodiment, to generate the full image of versionV2 of Virtual Machine C, a base image (e.g., the base image associatedwith Version VY of Virtual Machine A) may be acquired, the data changesassociated with forward incremental Fl may be applied to the base imageto generate a first intermediate image, the data changes associated withforward incremental F5 may be applied to the first intermediate image togenerate a second intermediate image, and the data changes associatedwith forward incremental F6 may be applied to the second intermediateimage to generate the full image of version V2 of Virtual Machine C.

FIG. 2J depicts one embodiment of a set of files associated withmultiple virtual machine snapshots after a rebasing process has beenperformed using the set of files in FIG. 2G. The set of files may bestored using a distributed file system, such as distributed file system112 in FIG. 1C. The rebasing process may generate new files R12, R11,and Base2. As depicted, the set of files includes a set of reverseincrementals (R11-R12 and R1-R3), a full image (Base2), and a set offorward incrementals (F3 and F5-F7). In this case, a first version ofVirtual Machine B may be generated using a forward incremental F3 thatderives from Version VX of Virtual Machine A and a second version ofVirtual Machine C may be generated using forward incrementals F5-F6 thatare derived from Version VZ of Virtual Machine A. In one example,Virtual Machine B may have been initially cloned from Version VX ofVirtual Machine A and Virtual Machine C may have been initially clonedfrom version VZ of Virtual Machine A. Forward incremental file F7 mayinclude changes to Version VW of Virtual Machine A that occurredsubsequent to the generation of the full image file Base2. In somecases, the forward incremental file F7 may comprise a writeable file orhave file permissions allowing modification of the file, while all otherfiles associated with earlier versions of Virtual Machine A compriseread only files.

FIG. 2K depicts one embodiment of a merged file for generating versionV1 of Virtual Machine B using the set of files depicted in FIG. 2J. Themerged file includes a first pointer (pBase2) that references the baseimage Base2, a second pointer (pR11) that references the reverseincremental R11, a third pointer (pR12) that references the reverseincremental R12, a fourth pointer (pR1) that references the reverseincremental R1, a fifth pointer (pR2) that references the reverseincremental R2, and a sixth pointer (pF3) that references the forwardincremental F3. In one embodiment, to generate the full image of versionV1 of Virtual Machine B, a base image (e.g., the base image associatedwith Version VW of Virtual Machine A) may be acquired, the data changesassociated with reverse incremental R11 may be applied to the base imageto generate a first intermediate image, the data changes associated withreverse incremental R12 may be applied to the first intermediate imageto generate a second intermediate image, the data changes associatedwith reverse incremental R1 may be applied to the second intermediateimage to generate a third intermediate image, the data changesassociated with reverse incremental R2 may be applied to the thirdintermediate image to generate a fourth intermediate image, and the datachanges associated with forward incremental F3 may be applied to thefourth intermediate image to generate the full image of version V1 ofVirtual Machine B.

FIG. 2L depicts one embodiment of a merged file for generating versionV2 of Virtual Machine C using the set of files depicted in FIG. 2J. Themerged file includes a first pointer (pBase2) that references the baseimage Base2, a second pointer (pR11) that references the reverseincremental R11, a third pointer (pF5) that references the forwardincremental F5, and a fourth pointer (pF6) that references the forwardincremental F6. In one embodiment, to generate the full image of versionV2 of Virtual Machine C, a base image (e.g., the base image associatedwith Version VW of Virtual Machine A) may be acquired, the data changesassociated with reverse incremental R11 may be applied to the base imageto generate a first intermediate image, the data changes associated withforward incremental F5 may be applied to the first intermediate image togenerate a second intermediate image, and the data changes associatedwith forward incremental F6 may be applied to the second intermediateimage to generate the full image of version V2 of Virtual Machine C.

In some cases, a backed-up version of a first virtual machine may begenerated by concurrently reading a full image of a second virtualmachine different from the first virtual machine from a first storagedevice (e.g., a HDD) while reading one or more incrementals associatedwith the first virtual machine from a second storage device (e.g., anSSD) different from the first storage device.

FIG. 2M depicts one embodiment of a set of files associated withmultiple virtual machine snapshots. The set of files may be stored usinga distributed file system, such as distributed file system 112 in FIG.1C. As depicted, the set of files includes a second full image (BaseB),a set of forward incrementals (F1-F2 and F5-F6) that derive from thesecond full image (BaseB), and a set of reverse incrementals (R1-R3)that derive from the second full image (BaseB). The set of files alsoincludes a first full image (BaseA) and a reverse incremental (R4) thatderives from the first full image (BaseA). In this case, the depictedsnapshots for Virtual Machine A include two different full imagesnapshots (BaseA and BaseB). Each of the full image snapshots maycomprise an anchor snapshot for a snapshot chain. The first full image(BaseA) and the reverse incremental (R4) may comprise a first snapshotchain with the first full image acting as the anchor snapshot. A secondsnapshot chain may comprise the second full image (BaseB), the set offorward incrementals (F1-F2), and the set of reverse incrementals(R1-R3). The first snapshot chain and the second snapshot chain may beindependent of each other and independently managed. For example, thebase image associated with the second snapshot chain for Virtual MachineA may be repositioned (e.g., via rebasing) without impacting the firstsnapshot chain for Virtual Machine A.

A third snapshot chain for Virtual Machine C may comprise the secondfull image (BaseB) and forward incrementals (F1 and F5-F6). The firstsnapshot chain for Virtual Machine A and the third snapshot chain forVirtual Machine C may be independent of each other and independentlymanaged. However, as Virtual Machine C is a dependent virtual machinethat depends from the second snapshot chain for Virtual Machine A,changes to the second snapshot chain may impact the third snapshotchain. For example, repositioning of the base image for the secondsnapshot chain due to rebasing may require the merged files for thethird snapshot chain to be updated.

In some embodiments, each of the snapshot chains for Virtual Machine Amay have a maximum incremental chain length (e.g., no more than 100total incremental files), a maximum reverse incremental chain length(e.g., no more than 50 reverse incremental files), and a maximum forwardincremental chain length (e.g., no more than 70 forward incrementalfiles. In the event that a new snapshot will cause one of the snapshotchains to violate the maximum incremental chain length, the maximumreverse incremental chain length, or the maximum forward incrementalchain length, then a new snapshot chain may be created for VirtualMachine A and a new full-image base file may be stored for the newsnapshot chain.

FIG. 2N depicts one embodiment of a merged file for generating versionVS of Virtual Machine A using the set of files depicted in FIG. 2M. Themerged file includes a first pointer (pBaseA) that references the firstbase image BaseA and a second pointer (pR4) that references the reverseincremental R4. In one embodiment, to generate the full image of versionVS of Virtual Machine A, the first base image associated with Version VTof Virtual Machine A may be acquired and the data changes associatedwith reverse incremental R4 may be applied to the first base image togenerate the full image of version VS of Virtual Machine A.

FIG. 2O depicts one embodiment of a merged file for generating versionVU of Virtual Machine A using the set of files depicted in FIG. 2M. Themerged file includes a first pointer (pBaseB) that references the secondbase image BaseB, a second pointer (pR1) that references the reverseincremental R1, a third pointer (pR2) that references the reverseincremental R2, and a fourth pointer (pR3) that references the reverseincremental R3. In one embodiment, to generate the full image of versionVU of Virtual Machine A, the second base image associated with VersionVY of Virtual Machine A may be acquired, the data changes associatedwith reverse incremental R1 may be applied to the second base image togenerate a first intermediate image, the data changes associated withreverse incremental R2 may be applied to the first intermediate image togenerate a second intermediate image, and the data changes associatedwith reverse incremental R3 may be applied to the second intermediateimage to generate the full image of version VU of Virtual Machine A.

FIG. 2P depicts one embodiment of a set of files associated withmultiple virtual machine snapshots after a rebasing process has beenperformed to a snapshot chain using the set of files in FIG. 2M. The setof files may be stored using a distributed file system, such asdistributed file system 112 in FIG. 1C. The rebasing process maygenerate new files R12, R11, and BaseB2. As depicted, the set of filesincludes a set of reverse incrementals (R11-R12 and R1-R2), a full image(BaseB2), and a set of forward incrementals (F5-F7). In this case, asecond version of Virtual Machine C may be generated using forwardincrementals F5-F6 that are derived from Version VZ of Virtual MachineA. Forward incremental file F7 may include changes to Version VW ofVirtual Machine A that occurred subsequent to the generation of the fullimage file BaseB2. In some cases, the forward incremental file F7 maycomprise a writeable file or have file permissions allowing modificationof the file, while all other files associated with earlier versions ofVirtual Machine A comprise read only files.

FIG. 2Q depicts one embodiment of a merged file for generating versionVU of Virtual Machine A using the set of files depicted in FIG. 2P. Themerged file includes a first pointer (pBaseA) that references the firstbase image BaseA and a second pointer (pF9) that references the forwardincremental F9. In one embodiment, to generate the full image of versionVU of Virtual Machine A, the first base image associated with Version VTof Virtual Machine A may be acquired and the data changes associatedwith forward incremental F9 may be applied to the first base image togenerate the full image of version VU of Virtual Machine A.

In some embodiments, upon detection that a second snapshot chain hasreached a maximum incremental chain length (e.g., no more than 500 totalincremental files), a maximum reverse incremental chain length (e.g., nomore than 400 reverse incremental files), or a maximum forwardincremental chain length (e.g., no more than 150 forward incrementalfiles), an existing snapshot chain (e.g., the first snapshot chaindepicted in FIG. 2P) may have its chain length extended or snapshotspreviously assigned to the second snapshot chain may be moved to theexisting snapshot chain. For example, the first snapshot chain depictedin FIG. 2M comprises two total snapshots, while the first snapshot chaindepicted in FIG. 2P comprises three total snapshots as the snapshotcorresponding with version VU of Virtual Machine A has moved from thesecond snapshot chain to the first snapshot chain.

In some embodiments, the number of snapshots in a snapshot chain maydecrease over time as older versions of a virtual machine areconsolidated, archived, deleted, or moved to a different storage domain(e.g., to cloud storage) depending on the data backup and archivingschedule for the virtual machine. In some cases, the maximum incrementalchain length or the maximum number of snapshots for a snapshot chain maybe increased over time as the versions stored by the snapshot chain age.In one example, if the versions of a virtual machine stored using asnapshot chain are all less than one month old, then the maximumincremental chain length may be set to a maximum of 200 incrementals;however, if the versions of the virtual machine stored using thesnapshot chain are all greater than one month old, then the maximumincremental chain length may be set to a maximum of 1000 incrementals.

In some embodiments, the maximum incremental chain length for a snapshotchain may be increased over time as the number of allowed snapshots in asnapshot chain may be increased as the backed-up versions of a virtualmachine get older. For example, the maximum incremental chain length fora snapshot chain storing versions of a virtual machine that are lessthan one year old may comprise a maximum incremental chain length of 200incrementals, while the maximum incremental chain length for a snapshotchain storing versions of a virtual machine that are more than one yearold may comprise a maximum incremental chain length of 500 incrementals.

In some embodiments, the maximum incremental chain length, the maximumreverse incremental chain length, or the maximum forward incrementalchain length for a snapshot chain may be adjusted over time as nodes ordisks are added to or removed from a cluster or upon an update to a databackup and archiving schedule for a virtual machine due to theassignment of a new backup class or a new backup, replication, andarchival policy. In one example, the maximum incremental chain lengthmay be increased from 200 incrementals to 500 incrementals if the numberof nodes or disks falls below a threshold number (e.g., is less thanfour nodes). In another example, the maximum incremental chain lengthmay be increased from 100 incrementals to 200 incrementals if theavailable disk storage falls below a threshold amount if disk space(e.g., the amount of available disk space is less than 20 TB).

FIG. 3A is a flowchart describing one embodiment of a process formanaging and storing virtual machine snapshots using a data storagesystem. In one embodiment, the process of FIG. 3A may be performed by astorage appliance, such as storage appliance 170 in FIG. 1A.

In step 302, a schedule for backing up a first virtual machine isdetermined. In one example, the schedule for backing up the firstvirtual machine may comprise periodically backing up the first virtualmachine every four hours. The schedule for backing up the first virtualmachine may be derived from a new backup, replication, and archivalpolicy or backup class assigned to the first virtual machine. In step304, a job scheduler is configured to implement the schedule for backingup the first virtual machine. In one example, a distributed jobscheduler, such as distributed job scheduler 108 in FIG. 1C, may beconfigured to schedule and run processes for capturing and storingimages of the first virtual machine over time according the schedule. Instep 306, a snapshot process for acquiring a snapshot of the firstvirtual machine is initiated. The snapshot process may send aninstruction to a virtualized infrastructure manager, such asvirtualization manager 169 in FIG. 1A, that requests data associatedwith the snapshot of the first virtual machine. In step 308, a type ofsnapshot to be stored is determined. The type of snapshot may comprise afull image snapshot or an incremental snapshot. In some cases, a fullimage snapshot may be captured and stored in order to serve as an anchorsnapshot for a new snapshot chain. Versions of the first virtual machinemay be stored using one or more independent snapshot chains, whereineach snapshot chain comprises a full image snapshot and one or moreincremental snapshots. One embodiment of a process for determining thetype of snapshot to be stored (e.g., storing either a full imagesnapshot or an incremental snapshot) is described later in reference toFIG. 3B.

In step 310, it is determined whether a full image of the first virtualmachine needs to be stored in order to store the snapshot of the firstvirtual machine. The determination of whether a full image is requiredmay depend on whether a previous full image associated with a priorversion of the first virtual machine has been acquired. Thedetermination of whether a full image is required may depend on thedetermination of the type of snapshot to be stored in step 308. If afull image needs to be stored, then step 311 is performed. Otherwise, ifa full image does not need to be stored, then step 312 is performed. Instep 311, the full image of the first virtual machine is acquired. Thefull image of the first virtual machine may correspond with a file orone or more data chunks. In step 312, changes relative to a priorversion of the first virtual machine or relative to another virtualmachine (e.g., in the case that the first virtual machine comprises adependent virtual machine whose snapshots derive from a full imagesnapshot of a second virtual machine different from the first virtualmachine) are acquired. The changes relative to the prior version of thefirst virtual machine or relative to a version of a different virtualmachine may correspond with a file or one or more data chunks. In step313, the full image of the first virtual machine is stored using adistributed file system, such as distributed file system 112 in FIG. 1C.In step 314, the changes relative to the prior version of the firstvirtual machine or relative to another virtual machine are stored usinga distributed file system, such as distributed file system 112 in FIG.1C. In one embodiment, the full image of the first virtual machine maybe stored using a first storage device of a first type (e.g., a HDD) andthe changes relative to the prior version of the first virtual machinemay be stored using a second storage device of a second type (e.g., anSSD).

In some embodiments, snapshots of the first virtual machine may beingested at a snapshot capture frequency (e.g., every 30 minutes) by adata storage system. When a snapshot of the first virtual machine isingested, the snapshot may be compared with other snapshots storedwithin the data storage system in order to identify a candidate snapshotfrom which the snapshot may depend. In one example, a scalableapproximate matching algorithm may be used to identify the candidatesnapshot whose data most closely matches the data associated with thesnapshot or to identify the candidate snapshot whose data has the fewestnumber of data differences with the snapshot. In another example, anapproximate matching algorithm may be used to identify the candidatesnapshot whose data within a first portion of the candidate snapshotmost closely matches data associated with a first portion of thesnapshot. In some cases, a majority of the data associated with thesnapshot and the candidate snapshot may be identical (e.g., both thesnapshot and the candidate snapshot may be associated with virtualmachines that use the same operation system and have the sameapplications installed). Once the candidate snapshot has beenidentified, then data differences (or the delta) between the snapshotand the candidate snapshot may be determined and the snapshot may bestored based on the data differences. In one example, the snapshot maybe stored using a forward incremental file that includes the datadifferences between the snapshot and the candidate snapshot. The forwardincremental file may be compressed prior to being stored within a filesystem, such as distributed file system 112 in FIG. 1C.

In step 316, a merged file associated with the snapshot is generated.The merged file may reference one or more files or one or more datachunks that have been acquired in either step 311 or step 312. In oneexample, the merged file may comprise a file or a portion of a file thatincludes pointers to the one or more files or the one or more datachunks. In step 318, the merged file is stored in a metadata store, suchas distributed metadata store 110 in FIG. 1C. In step 320, a virtualmachine search index for the first virtual machine is updated. Thevirtual machine search index for the first virtual machine may include alist of files that have been stored in the first virtual machine and aversion history for each of the files in the list. In one example, thevirtual machine search index for the first virtual machine may beupdated to include new files that have been added to the first virtualmachine since a prior snapshot of the first virtual machine was takenand/or to include updated versions of files that were previously storedin the first virtual machine.

FIG. 3B is a flowchart describing one embodiment of a process fordetermining the type of snapshot to be stored using a data storagesystem. The process described in FIG. 3B is one example of a process forimplementing step 308 in FIG. 3A. In one embodiment, the process of FIG.3B may be performed by a storage appliance, such as storage appliance170 in FIG. 1A.

In step 332, a snapshot chain for a first virtual machine is identified.The snapshot chain may comprise a full image snapshot for the firstvirtual machine and one or more incremental snapshots that derive fromthe full image snapshot. Backed-up versions of the first virtual machinemay correspond with one or more snapshot chains. Each of the one or moresnapshot chains may include a full image snapshot or a base image fromwhich incremental snapshots may derive. One example of backed-upversions of a virtual machine being stored using one or more snapshotchains is depicted in FIG. 2P in which the versions of Virtual Machine Aare stored using a first snapshot chain anchored by full image BaseA anda second snapshot chain anchored by full image BaseB2.

In step 334, it is determined whether the snapshot chain includes adependent base file. In this case, the first virtual machine maycomprise a dependent virtual machine that has snapshots that derive froma full image snapshot of a different virtual machine. In one embodiment,the first virtual machine and the different virtual machine from whichthe first virtual machine depends may each have different virtualmachine configuration files for storing configuration settings for thevirtual machines. In one example, the first virtual machine may have afirst number of virtual processors (e.g., two processors) and thedifferent virtual machine may have a second number of virtual processorsdifferent from the first number of virtual processors (e.g., fourprocessors). In another example, the first virtual machine may have afirst virtual memory size (e.g., 1 GB) and the different virtual machinemay have a second virtual memory size different from the first virtualmemory size (e.g., 2 GB). In another example, the first virtual machinemay run a first guest operating system and the different virtual machinemay run a second guest operating system different from the first guestoperating system.

In step 336, a maximum incremental chain length for the snapshot chainis determined based on whether the snapshot chain includes a dependentbase file. In one example, if the first virtual machine comprises adependent virtual machine, then the maximum incremental chain length maybe set to a maximum length of 200 snapshots; however if the firstvirtual machine is independent and is not a dependent virtual machine,then the maximum incremental chain length may be set to a maximum lengthof 500 snapshots.

In one embodiment, the maximum incremental chain length for the snapshotchain may be determined based on an age of the backed-up versions withinthe snapshot chain. In one example, the maximum incremental chain lengthfor a snapshot chain storing versions of the first virtual machine thatare less than one year old may comprise a maximum incremental chainlength of 100 incrementals, while the maximum incremental chain lengthfor a snapshot chain storing versions of the first virtual machine thatare more than one year old may comprise a maximum incremental chainlength of 200 incrementals.

In step 338, it is determined whether a new snapshot chain should becreated based on the maximum incremental chain length. In step 340, atype of snapshot to be stored for the first virtual machine isdetermined based on the maximum incremental chain length. The type ofsnapshot may comprise either a full image snapshot or an incrementalsnapshot. In one embodiment, if the snapshot chain for the first virtualmachine exceeds the maximum incremental chain length for the snapshotchain, then the type of snapshot to be stored for the first virtualmachine may comprise a full image snapshot. In this case, an additionalsnapshot chain may be created for the first virtual machine.

FIG. 3C is a flowchart describing one embodiment of a process forrestoring a version of a virtual machine using a data storage system. Inone embodiment, the process of FIG. 3C may be performed by a storageappliance, such as storage appliance 170 in FIG. 1A.

In step 382, a particular version of a virtual machine to be restored isidentified. In step 384, a base image from which the particular versionmay be derived is determined. In step 386, a set of incremental filesfor generating the particular version is determined. In one embodiment,the base image and the set of incremental files may be determined from amerged file associated with the particular version of the virtualmachine. In some cases, the set of incremental files may include one ormore forward incremental files and one or more reverse incrementalfiles. In step 388, a file associated with the particular version isgenerated using the base image and the set of incremental files. Thefile may be generated by patching the set of incremental files onto thebase image.

In one example, referring to FIG. 2G, if the particular versioncorresponds with Version V2 of Virtual Machine C, then the base imagemay correspond with the file Base in FIG. 2G and the set of incrementalfiles may correspond with files F1, F5, and F6 of FIG. 2G. In anotherexample, referring to FIG. 2G, if the particular version correspondswith Version V1 of Virtual Machine B, then the base image may correspondwith the file Base in FIG. 2G and the set of incremental files maycorrespond with files R1, R2, and F3 of FIG. 2G. In step 390, at least aportion of the file is outputted. The at least a portion of the file maybe electronically transferred to a computing device, such as computingdevice 154 in FIG. 1A, or to a virtualization manager, such asvirtualization manager 169 in FIG. 1A.

In some embodiments, the base image and a subset of the set ofincremental files may correspond with a second virtual machine differentfrom the virtual machine. In this case, the base image may comprise thebase image for the second virtual machine and the set of incrementalfiles may include a dependent base file that comprises data differencesbetween the base image for the second virtual machine and a previouslyacquired base image for the virtual machine. Data deduplicationtechniques may be applied to identify a candidate base image from whicha dependent base file may depend and to generate the dependent basefile.

FIG. 4A depicts one embodiment of a first set of files stored in a firststorage domain (Domain A) and a second set of files stored in a secondstorage domain (Domain B). The first set of files may correspond withdifferent point in time versions of a virtual machine, different pointin time versions of electronic file, or different point in time versionsof a database. In one embodiment, the different point in time versionsmay comprise different point in time versions of a virtual machinecaptured at times t045. In one example, versions V0-V5 of the virtualmachine may correspond with times t0-t5 or have been captured at timest045.

As depicted in FIG. 4A, the first set of files includes a first fullimage snapshot 410 (Fulls) and a first set of incremental files (filesI1-I5). The first set of incremental files may derive from the firstfull image snapshot. As an example, the first full image snapshot 410may correspond with the full image (Base) in FIG. 2A and the first setof incremental files may correspond with the foreword incrementals F1-F2in FIG. 2A. The second set of files includes a second full imagesnapshot 408 (Fulls) and a second set of incremental files (filesI1-I5). In one embodiment, the second set of files may be stored withina storage appliance, such as storage appliance 140 in FIG. 1A. Inanother embodiment, the second set of files may be stored using astorage appliance and the first set of files may be stored within acloud repository or within a remote cluster of data storage nodes. Inthis case, the second storage domain may correspond with the storageappliance and the first storage domain may correspond with the remotecluster of data storage nodes. In another embodiment, the first storagedomain may correspond with a first cluster of data storage nodes and thesecond storage domain may correspond with a second cluster of datastorage nodes. In one example, the first cluster of data storage nodesmay be associated with a first cloud-based data storage service and thesecond cluster of data storage nodes may be associated with a secondcloud-based data storage service. In another example, the first clusterof data storage nodes may be located within a first data center and thesecond cluster of data storage nodes may be located within a second datacenter. In some cases, the first storage domain may correspond with afirst cloud computing or data storage platform (e.g., Amazon WebServices®) and the second storage domain may correspond with a secondcloud computing or data storage platform (e.g., Microsoft Azure®). Thefirst storage domain and the second storage domain may comprise amulti-cloud environment. The first set of files and the second set offiles may correspond with replicated data files or archived data filesfor different point in time versions of a virtual machine that arestored using two or more different data storage domains.

In one embodiment, a storage appliance, such as storage appliance 140 inFIG. 1A, may acquire a full image snapshot and a first set ofincremental files corresponding with different point in time versions ofa virtual machine. As the point in time versions of the virtual machineage, the full image snapshot and the first set of incremental files maybe transferred to a second storage domain. In some cases, after thedifferent point in time versions of the virtual machine have beencaptured and stored for more than a threshold amount of time (e.g., areolder than a threshold number of days or have aged more than ten daysfrom being captured), the full image snapshot and a set of incrementalfiles that derive from the full image snapshot may be transferred to asecond storage domain or moved to cloud-based data storage. In oneexample, an archival threshold parameter for determining when to movefiles to the second storage domain or to cloud-based data storage may beset based on requirements from an SLA policy (e.g., specifying thatsnapshots older than ten days be moved to archival data storage).

FIG. 4B depicts one embodiment of the two data storage domains depictedin FIG. 4A in which a consolidation operation has been performed in onestorage domain (Domain A) of the two data storage domains. As depicted,a subset 402 of the first set of files comprising files I2-I4 storedusing the first storage domain (Domain A) have been consolidated to forma new incremental file 404 (I4′). The new incremental file 404 may begenerated by merging the subset 402 of the first set of files into asingle consolidated incremental file comprising data changes made to thevirtual machine between time t1 and time t4. In some cases, aconsolidation operation may be performed in only one of the two datastorage domains. Consolidation operations may be performed independentlydepending on the benefits (e.g., freeing up disk space) of performingthe consolidation operation within each of the data storage domains.

In one embodiment, the determination of whether to consolidate or mergetwo or more incremental files into a new incremental file may dependupon an amount of available disk space for storing files within aparticular storage domain, a combined disk size for the two or moreincremental files, an amount of disk space savings if the consolidationof the two or more incremental files is performed, an amount of CPUusage or available bandwidth, and/or the availability of processingresources within the particular storage domain to perform theconsolidation operation.

FIG. 4C depicts one embodiment of the two data storage domains depictedin FIG. 4B in which a third full image snapshot 406 (Full2) has beengenerated and stored to take the place of incremental file I4 in thesecond storage domain (Domain B). In one embodiment, the third fullimage snapshot 406 may be generated by combining the first full imagesnapshot 408 and the incremental files I1-I4 stored within the secondstorage domain. The third full image snapshot 406 may be generated bypatching the incremental files I1-I4 to the first full image snapshot408.

FIG. 4D depicts one embodiment of the two data storage domains depictedin FIG. 4C in which the incremental files I1-I4 stored within the secondstorage domain have been deleted and the first full image snapshot 408has been deleted. One benefit of generating and storing the third fullimage snapshot 406 within the second storage domain is that incrementalfiles corresponding with point in time versions occurring before theversion V4 of the virtual machine corresponding with the third fullimage snapshot 406 may be deleted to free-up disk space or to increasethe amount of available disk space within the second storage domain. Insome cases, the consolidation and/or deletion of files stored within thefirst storage domain and the second storage domain may be performedindependently such that the first storage domain may store a particularversion of a virtual machine (e.g., corresponding with time t4 in FIG.4D) using a first full image snapshot (e.g., full image snapshot 410 inFIG. 4D) and two forward incremental files (e.g., incremental files I1and I4′ in FIG. 4D), while the second storage domain may store theparticular version of the virtual machine (e.g., version V4) using onlya full image snapshot (e.g., full image snapshot 406 in FIG. 4D).

FIG. 4E depicts one embodiment of a set of files stored within a firststorage domain (Domain A). In one embodiment, the first storage domainmay correspond with a storage appliance, such as storage appliance 170in FIG. 1A. In another embodiment, the first storage domain maycorrespond with cloud-based data storage. The set of files includes afirst full image snapshot 416 (Full1) and a set of forward incrementalfiles (I1-I8) that derive from the first full image snapshot 416. Insome cases, a storage appliance may acquire and store snapshots of avirtual machine over time. As the snapshots age, electronic filescorresponding with the aged snapshots may be moved from the storageappliance to the first storage domain. An archival threshold parametermay be set to a particular number of days (e.g., seven days) such thatsnapshots of the virtual machine that are older than the particularnumber of days are moved or archived to the first storage domain. Forexample, the storage appliance may store 16 snapshots of the virtualmachine locally and then transfer nine snapshots of the virtual machinethat are older than seven days to the first storage domain. The ninesnapshots of the virtual machine that are older than seven days maycorrespond with the set of files depicted in FIG. 4E.

In some cases, an SLA policy may require that the three most recentsnapshots (e.g., corresponding with incremental files I6-I8) transferredto the first storage domain remain as individually accessible snapshots.The SLA policy may also provide that snapshots of the virtual machineolder than the three most recent snapshots stored within the firststorage domain must be retained at a particular frequency. In oneexample, the set of files stored within the first storage domain maycorrespond with daily snapshots of the virtual machine. The SLA policymay require that daily snapshots of the virtual machine be preserved forten days and thereafter one snapshot must be preserved every three days.In another example, the set of files stored within the first storagedomain may correspond with snapshots of a virtual machine taken everyeight hours for three days and then retaining one a day for one week.

FIG. 4F depicts one embodiment of the first storage domain of FIG. 4E inwhich two consolidation operations have been performed to generateincremental file 412 (I2′) and incremental file 414 (I5′). Theincremental file 412 may be generated by merging the incremental filesI1-I2 in FIG. 4E. The incremental file 414 may be generated by mergingthe incremental files I3-I5 in FIG. 4E. After the incremental files 412and 414 have been generated to preserve the point in time snapshotscorresponding with the incremental files I2 and I5 in FIG. 4E, theoriginal incremental files I1-I5 in FIG. 4E may be deleted from thefirst storage domain to free-up disk space. In some cases, theincremental file 412 may correspond with a version of a virtual machinethat has been pinned or prevented from being deleted (e.g., due to anapplication requiring that version of the virtual machine).

FIG. 4G depicts another embodiment of the first storage domain of FIG.4E in which a consolidated incremental file 412 (I2′) and a second fullimage snapshot 418 (Full2) have been generated and stored. Theincremental file 412 may be generated by merging the incremental filesI1-I2 in FIG. 4E. The second full image snapshot 418 may be generated bymerging the first full image snapshot 416 and the incremental filesI1-I5 in FIG. 4E. After patching the incremental files I1-I5 to thefirst full image snapshot 416 and storing the second full image snapshot418 within the first storage domain, the original incremental filesI1-I5 in FIG. 4E may be deleted from the first storage domain to free-updisk space. One benefit of generating the second full image snapshot 418is that the first full image snapshot 416 and the incremental file 412may be deleted after expiration without affecting the downstreamincremental files, such as incremental files I6-I8.

In one embodiment, computing resources within the first storage domainor accessible by the first storage domain (e.g., the first storagedomain may comprise a cloud-based data storage repository with access toan elastic compute cloud or to a cloud-based computing platform) may beused to generate the second full image snapshot 418 after acquiring thefirst full image snapshot 416 and the original incremental files I1-I5in FIG. 4E. In another embodiment, a storage appliance that captures orstores snapshots of the virtual machine may locally generate the secondfull image snapshot 418 and transfer the second full image snapshot 418to the first storage domain rather than transferring the incrementalfile corresponding with incremental file I5 in FIG. 4E. In one example,a storage appliance, such as storage appliance 170 in FIG. 1A, maygenerate and transfer full image snapshots of the virtual machine to thefirst storage domain on a periodic basis (e.g., once a day or every 100snapshots). In another example, a storage appliance may detect that acombined data size of a set of incremental files that have beentransferred to the first storage domain has exceeded a threshold datasize (e.g., the combined file sizes for the set of incremental files mayexceed 1 TB of data) and in response may generate and transfer a fullimage snapshot of the virtual machine to the first storage domain. Inthis case, the maximum data size between any two full image snapshots ofthe virtual machine within the first storage domain may be set orregulated by the storage appliance. After the full image snapshot of thevirtual machine has been transferred to the first storage domain,consolidation and deletion operations may be performed in order tofree-up disk space as the snapshots age within the first storage domain.

FIG. 4H depicts one embodiment of the first storage domain of FIG. 4G inwhich the archived snapshots older than the point in time correspondingwith the second full image snapshot 418 have been deleted. Thus, thesecond full image snapshot 418 comprises the oldest available snapshotwithin the first storage domain. Incremental files I9-I13 have beenarchived to the first storage domain.

FIG. 4I depicts one embodiment of the first storage domain of FIG. 4H inwhich a third full image snapshot 419 (Full3) has been generated andreplaced the incremental file 18 in the first storage domain. Theincremental files I8-I10 have been deleted from the first storagedomain. A consolidated incremental file I11′ has been generated bymerging incremental files I9-I11. The third full image snapshot 419 mayhave been generated in response to detecting that the total number ofexpired snapshots within the first storage domain that are older thanthe point in time corresponding with the third full image snapshot 419is greater than a threshold number of snapshots, that the amount ofavailable disk space for storing files within the first storage domainis below a threshold amount of disk space, and/or that the combined datasize of the expired snapshots within the first storage domain is greaterthan a threshold data size (e.g., more than 1 TB of disk space may bereclaimed by generating the third full image snapshot and deletingexpired snapshots older than the third full image snapshot).

FIG. 4J depicts one embodiment of the first storage domain of FIG. 4I inwhich incremental files I6-I7 and I12 have been deleted and the secondfull image snapshot 418 has been deleted in order to reclaim disk spacewithin the first storage domain.

In one embodiment, a hybrid local/remote data management system mayinclude a replication system that replicates data between a localstorage appliance and a remote storage appliance and/or a cloud-basedstorage service. The data may be deduplicated and compressed prior tobeing transferred from the local storage appliance to the remote storageappliance or the cloud-based storage service. In some embodiments, thelocal storage appliance may transfer or write full image snapshots andincremental files deriving from the full image snapshots to two or moreremote storage appliance and/or two or more cloud-based storageservices.

FIG. 5A is a flowchart describing one embodiment of a process forreclaiming disk space within an archival data source (or an archivaldata store). In one embodiment, the process of FIG. 5A may be performedby a storage appliance, such as storage appliance 170 or storageappliance 140 in FIG. 1A. The process of FIG. 5A may also be performedusing cloud-based computing resources or by generating and runningvirtual machines within a virtualized infrastructure.

In step 502, it is determined whether an archival data source has accessto compute resources. The archival data source may comprise a hardwaredata storage device, a storage area network storage device, anetworked-attached storage device, or a cloud-based data storage system.The archival data source may comprise a cloud-based data storageinfrastructure with the ability to instantiate virtual machines thathave the ability to modify data stored within the cloud-based datastorage infrastructure. If it is determined that the archival datasource has access to compute resources, then step 504 is performed.Otherwise, if it is determined that the archival data source does nothave access to the compute resources, then step 512 is performed. Instep 504, a first number of temporary virtual machines running on thecompute resources is determined. The first number of temporary virtualmachines may correspond with the number of virtual machines runningwithin a virtualized infrastructure for performing consolidation and/ordeletion of expired snapshots. In step 506, a second number of snapshotsthat have been transferred to the archival data source is determined. Inone example, the second number of snapshots may correspond with thenumber of snapshots that were transferred to the archival data sourcesince a last full image snapshot was uploaded. In step 507, an expireddata size for expired snapshots on the archival data source isdetermined. In some cases, the expired data size may correspond with themaximum amount of disk space that may be reclaimed on the archival datasource.

In step 508, it is detected that a temporary virtual machine should begenerated using the compute resources based on the first number oftemporary virtual machines running on the compute resources, the secondnumber of snapshots that were previously transferred to the archivaldata source, and/or the expired data size for the expired snapshots onthe archival data source. In one example, the temporary virtual machinemay be generated in response to detecting that the second number ofsnapshots that were previously transferred to the archival data sourcehas exceeded a threshold number of snapshots (e.g., 100 snapshots werepreviously transferred). In another example, the temporary virtualmachine may be generated in response to detecting that the expired datasize for the expired snapshots on the archival data source has exceededa threshold data size (e.g., is more than 500 GB). In step 510, aninstruction to cause the temporary virtual machine to be generated istransmitted. The instruction may be transmitted to a cloud-based datastorage infrastructure in order to generate the temporary virtualmachine within the cloud-based data storage infrastructure. In oneexample, the temporary virtual machine may comprise an instance of avirtual server for running applications within a virtualizedinfrastructure. The cloud-based data storage infrastructure may provideresizable compute capacity in the cloud. In some cases, the temporaryvirtual machine may correspond with a cloud computing instance (e.g., anEC2 instance) with access to cloud-based data storage (e.g., the S3cloud-based data storage service).

In step 512, a first number of full image snapshots being generated isdetermined. The first number of full image snapshots may correspond withthe number of full image snapshots being concurrently generated by astorage appliance, such as storage appliance 170 in FIG. 1A. In somecases, the number of full image snapshots being generated by a storageappliance or the number of full image snapshots that are beingtransferred to the archival data source may be restricted or limited(e.g., no more than four full image snapshots may be generated and/ortransferred from the storage appliance at the same time). In some cases,a distributed semaphore may be used to throttle or limit the number offull image snapshots that are generated and transferred to the archivaldata source. Before a new full image snapshot is generated, the job forgenerating the new full image snapshot may need to access the semaphore.If the job fails to allocate from the semaphore, then the job mayproceed and upload an incremental snapshot instead of the new full imagesnapshot.

In step 514, a second number of snapshots that were previouslytransferred to the archival data source is determined. In one example,the second number of snapshots may comprise the total number ofsnapshots that were previously transferred to the archival data sourceafter the last full image snapshots was transferred to the archival datasource (e.g., transferred to a cloud-based data storage repository). Instep 516, an expired data size for expired snapshots on the archivaldata source is determined. In step 518, it is detected that a full imagesnapshot should be generated and transferred to the archival data sourcebased on the first number, the second number, and the expired data size.In step 519, the full image snapshot is transferred to the archival datasource. In one embodiment, the full image snapshot may be generated andtransferred in response to detecting that the second number of snapshotsthat were previously transferred to the archival data source hasexceeded a threshold number of snapshots (e.g., 200 snapshots werepreviously transferred). In another embodiment, the full image snapshotmay be generated and transferred in response to detecting that theexpired data size for the expired snapshots on the archival data sourcehas exceeded a threshold data size (e.g., the expired data size isgreater than 1 TB).

FIG. 5B is a flowchart describing one embodiment of a process forgenerating one or more virtual machines for consolidating and/ordeleting expired snapshots. In one embodiment, the process of FIG. 5Bmay be performed by a storage appliance, such as storage appliance 170or storage appliance 140 in FIG. 1A. The process of FIG. 5B may also beperformed using cloud-based computing resources or by generating andrunning virtual machines within a virtualized infrastructure.

The process of FIG. 5B may be performed by a local storage appliancethat is used for capturing and storing snapshots of a virtual machine.The local storage appliance may control the generation of a temporaryvirtual machine within a cloud computing environment in order togenerate full image snapshots within the cloud computing environment,consolidate incremental files within the cloud computing environment,and delete expired snapshots within the cloud computing environment.

In step 522, a first full image snapshot and a first set of incrementalfiles associated with snapshots of a virtual machine are transmitted toa first domain. The first domain may comprise a cloud-based data storagedomain. In step 524, it is detected that a number of the snapshots ofthe virtual machine correspond with ages greater than a threshold age(e.g., more than 100 snapshots were captured more than three monthsago). In step 526, it is detected that an amount of disk space forstoring the first set of incremental files has exceeded a thresholdamount of disk space. In step 528, it is detected that a virtual machineinstance for consolidating a subset of the snapshots of the virtualmachine should be generated based on the number of the snapshots of thevirtual machine with ages greater than the threshold age and/or theamount of disk space for storing the first set of incremental files. Instep 530, an instruction is transmitted to the first domain to generatethe virtual machine instance for consolidating the subset of thesnapshots of the virtual machine. In one example, a cloud-based servicemay provide the ability to run virtual machine instances such that avirtual machine may be created or spun up to perform consolidationand/or deletion operations on archived data and then removed. In somecases, a previously uploaded image that contains the latest binaries forperforming the consolidation and/or deletion operations and variouscredentials for accessing the archived data may be used to launch thevirtual machine instance. In step 532, a completion of the consolidationof the subset of the snapshots of the virtual machine is detected. Instep 534, a second instruction is transmitted to the first domain toterminate the virtual machine instance.

FIG. 5C is a flowchart describing one embodiment of a process forconsolidating expired snapshots. In one embodiment, the process of FIG.5C may be performed by a storage appliance, such as storage appliance170 or storage appliance 140 in FIG. 1A. The process of FIG. 5C may beperformed using cloud-based computing resources or by generating andrunning virtual machines within a virtualized infrastructure.

In step 542, a first full image snapshot and a first set of incrementalfiles associated with versions of the virtual machine are acquired. Thefirst full image snapshot may correspond with full image snapshot 416stored using the first storage domain in FIG. 4E and the first set ofincremental files may correspond with incremental files I1-I8 storedusing the first storage domain in FIG. 4E. In step 544, the first fullimage snapshot and the first set of incremental files are stored. Instep 546, it is detected that an amount of available disk space is belowa threshold amount of disk space. In one example, it may be detectedthat the amount of available disk space within a first storage domain isless than 10 TB. In step 548, it is detected that a number of theversions of the virtual machine correspond with ages exceeding athreshold age. In one example, it may be detected that at least 20snapshots of the virtual machine correspond with versions that are morethan one month old.

In step 550, it is determined whether a second full image snapshot needsto be generated for storing a second subset of the first set ofincremental files. In some cases, the second full image snapshot mayallow a dependency chain to be broken and allow the second subset of thefirst set of incremental files to be stored while a first subset of thefirst set of incremental files is deleted or no longer accessible. Inone example, the first set of incremental files may correspond withincremental files I1-I8 stored using the first storage domain in FIG.4E, the first subset of the first set of incremental files maycorrespond with incremental files I1-I4, and the second subset of thefirst set of incremental files may correspond with incremental filesI5-I8. The determination of whether the second full image snapshot needsto be generated may depend on an amount of available disk space forstoring the second subset of the first set of incremental files and/orthe first subset of the first set of incremental files (e.g., the amountof available disk space within a data storage device comprising a firststorage domain), a virtual machine change rate for the virtual machine,detection of an increase in the amount of data changes occurring to thevirtual machine, the total number of snapshots captured for the virtualmachine, and/or a combined data size for the first set of incrementalfiles. If it is determined that the second full image snapshot needs tobe generated, then step 551 is performed. Otherwise, if it is determinedthat the second full image snapshot does not need to be generated, thenstep 554 is performed.

In step 551, the second full image snapshot is identified. In oneembodiment, the second full image snapshot may be identified as theoldest snapshot that has not yet expired or the oldest snapshot of avirtual machine that cannot be deleted and must be recoverable. Inanother embodiment, the second full image snapshot may be identified asthe next snapshot of a virtual machine to be archived or transferredfrom a first data storage domain to a second data storage domain. Instep 552, the second full image snapshot is generated. In one example,the second full image snapshot may correspond with full image snapshot418 in FIG. 4G. The second full image snapshot may be generated byapplying incremental files to the first full image snapshot. In oneexample, the second full image snapshot 418 in FIG. 4G may be generatedby applying or patching incremental files I1-I5 in FIG. 4E to the firstfull image snapshot 416 in FIG. 4E.

In step 553, the second full image snapshot is stored. The second fullimage snapshot may be stored using a volatile memory or a non-volatilememory. The second full image snapshot may be stored using a HDD or anSSD. In step 554, a consolidated incremental file is generated. In step555, the consolidated incremental file is stored. In one example, theconsolidated incremental file may correspond with incremental file 414in FIG. 4F and the consolidated incremental file may be generated bymerging incremental files I3-I5 in FIG. 4E. In step 556, a first subsetof the first set of incremental files is deleted. In one example, thefirst set of incremental files may correspond with incremental filesI1-I8 in FIG. 4E. The first subset of the first set of incremental filesmay comprise incremental files I3-I4 in FIG. 4E and the second subset ofthe first set of incremental files may comprise incremental files I6-I8in FIG. 4E. In step 558, the second full image snapshot or theconsolidated incremental file may be outputted. The second full imagesnapshot may be outputted by transferring the second full image snapshotor a portion of the second full image snapshot to a hardware datastorage device, a computing device, or to cloud-based data storage.

In one embodiment, the second full image snapshot may be generated by astorage appliance, such as storage appliance 170 in FIG. 1A, andtransmitted from the storage appliance to a remote storage appliance orto cloud-based data storage. In another embodiment, the consolidatedincremental file may be generated by the storage appliance andtransmitted from the storage appliance to the remote storage applianceor to cloud-based data storage.

FIG. 5D is a flowchart describing one embodiment of a process forgenerating one or more full image snapshots to enable deletion ofexpired snapshots. In one embodiment, the process of FIG. 5D may beperformed by a storage appliance, such as storage appliance 170 orstorage appliance 140 in FIG. 1A. The process of FIG. 5D may also beperformed using cloud-based computing resources or by generating andrunning virtual machines within a virtualized infrastructure.

The process of FIG. 5D may be performed by a local storage appliancethat is used for capturing and storing snapshots of a virtual machine.The local storage appliance may control the generation and uploading ofperiodic full image snapshots in order to facilitate the deletion ofexpired snapshots within an archival data source.

In step 562, a first full image snapshot and a first set of incrementalfiles associated with a first set of versions of a virtual machine areacquired. In step 564, the first full image snapshot and the first setof incremental files are stored. In one example, the first full imagesnapshot may correspond with the first full image snapshot 416 in FIG.4E and the first set of incremental files may correspond withincremental files I1-I4 in FIG. 4E. In step 566, the first full imagesnapshot and the first set of incremental files are transferred to afirst domain. In one example, the first domain may correspond with thefirst storage domain (Domain A) in FIG. 4E. In step 568, a second set ofincremental files associated with a second set of versions of thevirtual machine are acquired. The second set of versions of the virtualmachine may comprise point in time versions of the virtual machine thatare captured subsequent to the first set of versions of the virtualmachine. In one embodiment, a storage appliance, such as storageappliance 170 in FIG. 1A, may acquire the first set of incremental filesand the second set of incremental files from a server, such as server160 FIG. 1A. The first set of incremental files may correspond withincremental files I1-I4 in FIG. 4E and the second set of incrementalfiles may correspond with incremental files I5-I8 in FIG. 4E.

In step 570, it is detected that a number of the first set ofincremental files and/or the second set of incremental files is greaterthan a threshold number of incremental files. In one example, it may bedetected that the combined number of the first set of incremental filesand the second set of incremental files acquired from a server isgreater than the threshold number of incremental files (e.g., is greaterthan 100 incremental files). In step 572, it is detected that an amountof disk space for storing the first set of incremental files and/or thesecond set of incremental files has exceeded a threshold amount of diskspace. In one example, it may be detected that the amount of disk spacefor storing the first of incremental files and the second set ofincremental files using a storage appliance has exceeded the thresholdamount of disk space (e.g., is greater than 1 TB of disk space).

In step 574, a second full image snapshot corresponding with a secondversion of the virtual machine is generated using at least a subset ofthe second set of incremental files and the first full image snapshot.The second full image snapshot may correspond with the second full imagesnapshot 418 in FIG. 4G, the subset of the second set of incrementalfiles may correspond with the incremental file I5 in FIG. 4E, and thefirst full image snapshot may correspond with the first full imagesnapshot 416 in FIG. 4E. In step 576, the second full image snapshot isstored. In some cases, a storage appliance may store or retain thesecond full image snapshot even after the second full image snapshot hasbeen transferred to a first storage domain for archiving (e.g., to afirst cloud-based data storage service). In step 578, the second fullimage snapshot is transferred to the first domain. The second full imagesnapshot may be outputted or electronically transmitted to a serverwithin the first domain. In one example, the first domain may comprise aportion of a data center and the second full image snapshot may betransmitted to a server within the data center used for managing,archiving, or storing snapshots of virtual machines. In some cases, afull upload threshold parameter for determining when to generate andupload a full image snapshot to a data archival source may be set basedon a snapshot frequency for capturing snapshots of a real or virtualmachine or based on requirements from an SLA policy assigned to the realor virtual machine.

In one embodiment, the second full image snapshot may be generated anduploaded to a data archival source in response to detecting that thenumber of the first set of incremental files and the second set ofincremental files is greater than the threshold number of incrementalfiles. In another embodiment, the second full image snapshot may begenerated and uploaded to a data archival source in response todetecting that the amount of disk space for storing the first set ofincremental files and the second set of incremental files has exceededthe threshold amount of disk space. In another embodiment, the secondfull image snapshot may be generated and uploaded to a data archivalsource in response to detecting that the combined file sizes of thefirst set of incremental files and/or the second set of incrementalfiles has exceeded a threshold data size (e.g., has exceeded 1 TB). Inanother embodiment, the second full image snapshot may be generated anduploaded to a data archival source in response to detecting that thecombined data size for the first set of incremental files and the secondset of incremental files has exceeded a threshold fraction of a filesize corresponding with the first full image snapshot. In one example,the first full image snapshot may comprise a file of size 1 TB and thesecond full image snapshot may be generated in response to detectingthat the combined data size of the first set of incremental files andthe second set of incremental files is greater than 50% of the file sizefor the first full image snapshot (i.e., the combined data size isgreater than 500 GB if the first full image snapshot comprises 1 TB ofdata). In some cases, the second full image snapshot may be generatedand uploaded to a data archival source in response to detecting that acombined data size associated with incremental files transmitted from astorage appliance to a remote storage appliance or transmitted to afirst cloud-based data storage service has exceeded a threshold datasize (e.g., is greater than 500 GB).

FIG. 6A depicts one embodiment of a first set of point in time versionsof a virtual machine that have been stored using a first storage domain(Domain A) and a second set of point in time versions of the virtualmachine that have been stored using a second storage domain (Domain B).The initial version of the virtual machine may correspond with versionV0 of the virtual machine and the most recent version of the virtualmachine may correspond with version V22 of the virtual machine. Asdepicted, the first 16 versions of the virtual machine correspondingwith versions V0-V15 have been stored using the first storage domain andthe last seven versions of the virtual machine corresponding withversions V16-V22 have been stored using the second storage domain. Inorder to transfer version V16 612 of the virtual machine from the secondstorage domain to the first storage domain, a first incremental filecorresponding with the data differences 602 between version V16 612 andversion V15 616 may be transferred from the second storage domain to thefirst storage domain. The first incremental file may comprise anin-order incremental file.

An incremental file may include the changed data blocks between twodifferent versions of the virtual machine. The incremental file may becompressed prior to transmission to the first storage domain. Theincremental file may have an associated fingerprint file that includessignatures for each of the changed data blocks. The signatures may begenerated using a fingerprinting algorithm such as the Rabin fingerprintalgorithm or a cryptographic hashing algorithm (e.g., MD5 or one of theSHA-family of algorithms). In one example, a virtual disk of the virtualmachine may be partitioned into a plurality of blocks (e.g., blocks with64 MB sizes) and signatures may be generated for each of the pluralityof blocks.

In order to transfer the most recent version of the virtual machine fromthe second storage domain (e.g., a local storage appliance) to the firststorage domain (e.g., a cloud-based data storage service), a secondincremental file corresponding with the data differences 604 betweenversion V22 614 and version V15 616 may be transferred from the secondstorage domain to the first storage domain. The second incremental filemay comprise an out-of-order incremental file.

FIG. 6B depicts one embodiment of a first set of files stored in thefirst storage domain (Domain A) and a second set of files stored in thesecond storage domain (Domain B). The first set of files may correspondwith the versions V0-V15 of the virtual machine depicted in FIG. 6A. Thesecond set of files may correspond with the versions V16-V22 of thevirtual machine depicted in FIG. 6A. The first full image snapshot 642(Full1) may comprise a full image snapshot of version V0 610 of thevirtual machine. The version V15 616 of the virtual machine may begenerated by patching incremental file 644 (I15) to incremental filesI1-I14 and the first full image snapshot 642. The version V16 612 of thevirtual machine may correspond with incremental file 646 (I16), whichmay comprise data differences between version V15 616 and version V16612 of the virtual machine. The version V22 614 of the virtual machinemay correspond with incremental file 648 (I22), which may comprise datadifferences between version V22 614 and version V21 of the virtualmachine.

FIG. 6C depicts one embodiment of the different versions of the virtualmachine depicted in FIG. 6A in which an out-of-order incremental filehas been transferred from the second storage domain to the first storagedomain. FIG. 6D depicts one embodiment of two sets of files used forstoring the versions of the virtual machine depicted in FIG. 6C withinthe two different data storage domains. Version V22 of the virtualmachine now resides in both the first storage domain and the secondstorage domain due to the transfer of the out-of-order incremental file.Version V22 618 in the first storage domain of FIG. 6C may correspondwith incremental file 652 (I22′) in FIG. 6D and version V22 614 in thesecond storage domain of FIG. 6C may correspond with incremental file648 (I22) in FIG. 6D. Version V22 618 in the first storage domain ofFIG. 6C and version V22 614 in the second storage domain of FIG. 6C maycomprise the same point in time version of the virtual machine. Theversion V22 618 of the virtual machine in the first storage domain maybe generated by patching incremental files I1-I15 and 122′ to the firstfull image snapshot 642. The version V22 614 of the virtual machine inthe second storage domain may be generated by patching incremental filesI1-I15 in the first storage domain and incremental files I16-I21 in thesecond storage domain to the first full image snapshot 642.

In one embodiment, on a periodic basis (e.g., every night at 11 PM), themost recent version of the virtual machine may be transferred from thesecond storage domain to the first storage domain. The most recentversion of the virtual machine may be transferred to the first storagedomain by identifying a version of the virtual machine that is storedwithin the first storage domain and determining an out-of-orderincremental file corresponding with data differences between the versionof the virtual machine stored within the first storage domain and themost recent version of the virtual machine stored within the secondstorage domain.

FIG. 6E depicts one embodiment of the different versions of the virtualmachine depicted in FIG. 6C in which version V16 of the virtual machinehas been transferred or archived from the second storage domain to thefirst storage domain. FIG. 6F depicts one embodiment of two sets offiles used for storing the versions of the virtual machine depicted inFIG. 6E within the two different data storage domains. In oneembodiment, an in-order incremental file corresponding with datadifferences between the version V16 622 of the virtual machine andversion V15 616 of the virtual machine may be transferred from thesecond storage domain to the first storage domain. In anotherembodiment, an out-of-order incremental file corresponding with datadifferences between version V16 622 of the virtual machine and versionV22 618 of the virtual machine may be transferred from the secondstorage domain to the first storage domain. The determination of whetherto transfer the in-order incremental file or the out-of-orderincremental file may depend on the file size or the data size for theincremental files. In one example, if the out-of-order incremental filecomprises a smaller file size or a smaller data size than the in-orderincremental file, then the out-of-order incremental file may betransferred to the first storage domain in order to conserve disk spacewithin the first storage domain. In another example, if the in-orderincremental file has a first file size and the out-of-order incrementalfile has a second file size, then the in-order incremental file may betransferred to the first storage domain if the first file size is lessthan the second file size. If the out-of-order incremental file iscomparable in size or equal in size to the in-order incremental file,then it may be preferable to transfer the out-of-order incremental fileas a later version of the virtual machine will likely expire later(e.g., version V22 618 of the virtual machine will likely expire afterversion V15 616 of the virtual machine expires).

Version V16 622 in the first storage domain of FIG. 6E may correspondwith incremental file 654 (I16′) in FIG. 6F. In one embodiment, theincremental file 654 (I16′) may include data differences between versionV16 622 of the virtual machine and version V22 618 of the virtualmachine. The incremental file 654 may include one or more changed datablocks in which data changes occurred to the virtual machine betweenversion V16 of the virtual machine and version V22 of the virtualmachine. The version V16 622 of the virtual machine in the first storagedomain may be generated by patching incremental files I1-I15, 122′, andI16′ to the first full image snapshot 642.

FIG. 6G depicts one embodiment of the different versions of the virtualmachine depicted in FIG. 6E in which version V22 of the virtual machinehas been transferred or archived from the second storage domain to thefirst storage domain. FIG. 6H depicts one embodiment of two sets offiles used for storing the versions of the virtual machine depicted inFIG. 6G within the two different data storage domains. In oneembodiment, an in-order incremental file corresponding with version V22of the virtual machine has been transferred to the first storage domain.

Version V22 614 in the first storage domain of FIG. 6G may correspondwith incremental file 662 (I22) in FIG. 6H. The incremental file 662(I22) may include data differences between version V22 614 of thevirtual machine and version V21 of the virtual machine. The incrementalfile 662 may include one or more changed data blocks in which datachanges occurred to the virtual machine between version V21 of thevirtual machine and version V22 of the virtual machine. The incrementalfile 652 (I22′) in FIG. 6D may be deleted from the first storage domain.Versions V23-V29 of the virtual machine in FIG. 6G may correspond withincremental files I23-I29 stored using the second storage domain in FIG.6H. The most recent snapshot of the virtual machine may comprise versionV29 634 of the virtual machine that corresponds with incremental file668 (I29). The next snapshot of the virtual machine to be transferredfrom the second storage domain to the first storage domain may compriseversion V23 632 of the virtual machine that corresponds with incrementalfile 669 (I23). The in-order incremental file 664 (I16) in the firststorage domain depicted in FIG. 6H may have replaced the out-of-orderincremental file 654 (I16′) in the first storage domain depicted in FIG.6F.

FIG. 6I depicts one embodiment of the different versions of the virtualmachine depicted in FIG. 6A in which version V22 of the virtual machineneeds to be transferred from the second storage domain to the firststorage domain prior to being archived. In some cases, a firstincremental file corresponding with data changes or data differences 602that occurred between version V15 616 of the virtual machine and V16 612of the virtual machine and a second incremental file corresponding withdata changes or data differences 674 that occurred between version V22614 of the virtual machine and V16 612 of the virtual machine may begenerated and transferred to the first storage domain.

FIG. 6J depicts one embodiment of the different versions of the virtualmachine depicted in FIG. 6I in which version V16 676 and version V22 678have been moved or transferred to the first storage domain. In oneembodiment, the first incremental file corresponding with datadifferences 602 that occurred between version V15 616 of the virtualmachine and V16 612 of the virtual machine may be transferred as a fullimage snapshot for version V16 of the virtual machine. The secondincremental file corresponding with data differences 674 that occurredbetween version V22 614 of the virtual machine and V16 612 of thevirtual machine may be transferred as an incremental snapshot forversion V22 of the virtual machine. In another embodiment, both thefirst incremental file and the second incremental file may betransferred as incremental snapshot files. Both the first incrementalfile and the second incremental file may be concurrently generatedand/or transferred to the first storage domain.

FIG. 7A is a flowchart describing one embodiment of a process fortransferring snapshots of a virtual machine from a first storage domainto a second storage domain. In one embodiment, the process of FIG. 7Amay be performed by a storage appliance, such as storage appliance 170or storage appliance 140 in FIG. 1A. The process of FIG. 7A may also beperformed using cloud-based computing resources or by generating andrunning virtual machines within a virtualized infrastructure.

In step 702, a first incremental file corresponding with datadifferences between a first snapshot of a virtual machine and a secondsnapshot of the virtual machine are acquired. The first incremental filemay correspond with data differences between a first point in timeversion of the virtual machine and a second point in time version of thevirtual machine that is captured or acquired subsequent to the firstpoint in time. In step 704, the first incremental file is stored withinthe first storage domain. In step 706, it is detected that the secondsnapshot of the virtual machine stored within the first storage domainshould be transmitted to a second storage domain. In one example, thesecond snapshot of the virtual machine may comprise the most recentsnapshot of the virtual machine. In step 708, an anchor snapshot storedwithin the second storage domain is identified. In one example, thesecond snapshot of the virtual machine may correspond with version V22614 of the virtual machine in FIG. 6A and the anchor snapshot maycorrespond with version V15 616 of the virtual machine in FIG. 6A. Inone embodiment, the anchor snapshot stored within the second storagedomain may be identified as the last uploaded snapshot to the secondstorage domain. In another embodiment, the anchor snapshot stored withinthe second storage domain may be identified as one of the last tensnapshots uploaded to the second storage domain in which the fewestnumber of changed blocks have occurred between a version of the virtualmachine corresponding with the second snapshot and another version ofthe virtual machine corresponding with the anchor snapshot.

In step 710, a second incremental file corresponding with datadifferences between the anchor snapshot and the second snapshot of thevirtual machine is generated. The second incremental file may correspondwith incremental file 652 (I22′) in FIG. 6D. The second incremental filemay include one or more changed data blocks that changed between a firstpoint in time version of the virtual machine associated with the anchorsnapshot and a second point in time version of the virtual machineassociated with the second snapshot. In some cases, the anchor snapshotmay be acquired from the second storage domain prior to generating thesecond incremental file. In other cases, the anchor snapshot may residewithin the first storage domain as the last updated snapshot transferredto the second storage domain may not have been deleted from the firststorage domain.

In step 712, the second incremental file is transmitted to the secondstorage domain. In one example, the second incremental file may beelectronically transferred from a local storage appliance to a remotestorage appliance. In another example, the second incremental file maybe electronically transferred from a local storage appliance, such asstorage appliance 170 in FIG. 1A, to cloud-based data storage or cloudstorage. In step 714, it is detected that the second snapshot of thevirtual machine stored within the first storage domain should bearchived to the second storage domain. In step 716, it is detected thata disk size of the second incremental file is greater than a disk sizeof the first incremental file. In step 718, the first incremental fileis transferred to the second storage domain. The first incremental filemay be transferred to the second storage domain in response to detectingthat the disk size (or file size) of the second incremental file isgreater than the disk size (or file size) of the first increment fileand/or in response to detecting that the second snapshot of the virtualmachine should be archived to the second storage domain. In step 720,the second incremental file is deleted from the second storage domain.In some cases, the second incremental file may be replaced by the firstincremental file in order to reduce the amount of disk space required tostore the second snapshot of the virtual machine within the secondstorage domain.

In some embodiments, on a periodic basis (e.g., every 24 hours), themost recent version of a virtual machine may be transferred to anarchival data source (e.g., to cloud storage) prematurely in order toallow testing or development of the most recent version of the virtualmachine to be performed directly from the archival data source. Overtime, the most recent version of the virtual machine that wastransferred to the archival data source will age and eventually be movedor archived from the first storage domain to the archival data source(or to a second storage domain) depending on an archival threshold(e.g., snapshots that are more than ten days old may be archived fromthe first storage domain to the archival data source). When it comestime to transfer the aged snapshot to the archival data source, adecision may be made to either keep the already transferred out-of-orderincremental file for the aged snapshot or to transfer an in-orderincremental file for the aged snapshot.

In one example, the in-order incremental file may be transferred to thesecond storage domain if a file size of the in-order incremental file isless than a file size of the out-of-order incremental file. Bytransferring the in-order incremental file to the first storage domain,a disk space reduction may occur by deleting the out-of-orderincremental file from the first storage domain. In another example, if athreshold number of snapshots has occurred between the anchor snapshotand the second snapshot, then the in-order incremental file may betransferred to the second storage domain. In this case, as theout-of-order incremental file includes data changes relative to anearlier version of the virtual machine as compared with the in-orderincremental file, transferring the in-order incremental file may allowadditional expired snapshots to be deleted within the first storagedomain. In another example, if a threshold time difference has occurredbetween the anchor snapshot and the second snapshot (e.g., thedifference in time between the anchor snapshot and the second snapshotis more than one week), then the in-order incremental file may betransferred to the second storage domain.

FIG. 7B is a flowchart describing another embodiment of a process fortransferring snapshots of a virtual machine from a first storage domainto a second storage domain. In one embodiment, the process of FIG. 7Bmay be performed by a storage appliance, such as storage appliance 170or storage appliance 140 in FIG. 1A. The process of FIG. 7B may also beperformed using cloud-based computing resources or by generating andrunning virtual machines within a virtualized infrastructure.

In step 732, a first incremental file corresponding with datadifferences (or data changes) between a first snapshot of a virtualmachine and a second snapshot of the virtual machine are acquired. Instep 734, the first incremental file is stored within the first storagedomain. In step 736, it is detected that the first snapshot of thevirtual machine stored within the first storage domain should betransmitted to a second storage domain. In one example, the firstsnapshot of the virtual machine may comprise a recent snapshot of thevirtual machine (e.g., the most recently captured snapshot of thevirtual machine) that has not yet been archived or transferred to thesecond storage domain. The second storage domain may act as an archivaldata source. In step 738, an anchor snapshot stored within the firststorage domain is identified. In one example, the anchor snapshot may beidentified as the oldest snapshot stored within the first storagedomain. In another example, the anchor snapshot may be identified as thenext snapshot that is to be archived to the second storage domain.

In step 740, a second incremental file corresponding with datadifferences between the anchor snapshot and the first snapshot of thevirtual machine is generated. In step 742, the second incremental fileand a third incremental file associated with the anchor snapshot aretransferred or transmitted to the second storage domain. In one example,the anchor snapshot may correspond with version V16 of the virtualmachine in FIG. 6J and the first snapshot may correspond with versionV22 of the virtual machine in FIG. 6J.

In step 744, it is detected that a data size of the second incrementalfile is greater than a data size of the first incremental file. In thiscase, an in-order incremental file corresponding with version V22 614 ofthe virtual machine in FIG. 6J may have a smaller file size or consumeless disk space than an out-of-order incremental file corresponding withversion V22 676 of the virtual machine in FIG. 6J. In step 746, thefirst incremental file is transferred to the second storage domain inresponse to detecting that the data size of the second incremental fileis greater than the data size of the first incremental file. In step748, the second incremental file is deleted from the second storagedomain. In this case, transferring the first incremental file to thesecond storage domain and deleting the second incremental file from thesecond storage domain may free up disk space within the second storagedomain.

One embodiment of the disclosed technology includes acquiring a firstfull image snapshot and a set of incremental files corresponding withdifferent point in time versions of a virtual machine, storing the firstfull image snapshot and the set of incremental files, detecting that adata size for a first subset of the set of incremental files hasexceeded a threshold data size, generating a second full image snapshotusing the first full image snapshot and the first subset of the set ofincremental files in response to detecting that the data size for thefirst subset of the set of incremental files has exceeded the thresholddata size, and replacing a first incremental file of the first subset ofthe set of incremental files with the second full image snapshot.

One embodiment of the disclosed technology includes acquiring a firstincremental file corresponding with data differences between a firstsnapshot of a virtual machine and a second snapshot of the virtualmachine, storing the first incremental file within a first data storagedomain, detecting that the first snapshot of the virtual machine shouldbe transmitted to a second data storage domain different from the firstdata storage domain, identifying an anchor snapshot stored within thefirst data storage domain, generating a second incremental filecorresponding with data differences between the anchor snapshot and thefirst snapshot of the virtual machine, and transmitting the secondincremental file and a third incremental file associated with the anchorsnapshot to the second data storage domain.

One embodiment of the disclosed technology includes a memory (e.g., avolatile or non-volatile memory) in communication with one or moreprocessors. The memory configured to store a first full image snapshotand a set of incremental snapshots corresponding with different point intime versions of a virtual machine. The one or more processorsconfigured to detect that a data size for a first subset of the set ofincremental snapshots has exceeded a threshold data size and generate asecond full image snapshot using the first full image snapshot and thefirst subset of the set of incremental snapshots in response todetection that the data size for the first subset of the set ofincremental snapshots has exceeded the threshold data size. The one ormore processors configured to store the second full image snapshot anddelete a first incremental snapshot of the first subset of the set ofincremental snapshots subsequent to the second full image snapshot beingstored.

One embodiment of the disclosed technology includes a memory (e.g., avolatile or non-volatile memory) in communication with one or moreprocessors. The memory configured to store a first incremental filecorresponding with data differences between a first snapshot of avirtual machine and a second snapshot of the virtual machine. The one ormore processors configured to detect that the first snapshot of thevirtual machine should be transmitted from a first data storage domainto a second data storage domain and identify an anchor snapshot residingwithin the first data storage domain. The one or more processorsconfigured to generate a second incremental file corresponding with datadifferences between the anchor snapshot and the first snapshot of thevirtual machine and transmit the second incremental file and a thirdincremental file associated with the anchor snapshot to the secondstorage domain.

One embodiment of the disclosed technology includes acquiring a firstfull image snapshot and a first set of incremental files associated witha first set of versions of a real or virtual machine from a computingdevice, storing the first full image snapshot and the first set ofincremental files associated with the first set of versions of the realor virtual machine, transferring the first full image snapshot and thefirst set of incremental files associated with the first set of versionsof the real or virtual machine to an archival source, acquiring a secondset of incremental files associated with a second set of versions of thevirtual machine from the computing device, detecting that a data sizecorresponding with the first set of incremental files and the second setof incremental files has exceeded a threshold data size, and generatinga second full image snapshot corresponding with a second version of thereal or virtual machine in response to detecting that the data sizecorresponding with the first set of incremental files and the second setof incremental files has exceeded the threshold data size. Thegenerating the second full image includes applying at least a subset ofthe second set of incremental files and the first set of incrementalfiles to the first full image snapshot. The method further comprisesstoring the second full image snapshot corresponding with the secondversion of the real or virtual machine and transferring the second fullimage snapshot to the archival source.

The disclosed technology may be described in the context ofcomputer-executable instructions, such as software or program modules,being executed by a computer or processor. The computer-executableinstructions may comprise portions of computer program code, routines,programs, objects, software components, data structures, or other typesof computer-related structures that may be used to perform processesusing a computer. In some cases, hardware or combinations of hardwareand software may be substituted for software or used in place ofsoftware.

Computer program code used for implementing various operations oraspects of the disclosed technology may be developed using one or moreprogramming languages, including an object oriented programming languagesuch as Java or C++, a procedural programming language such as the “C”programming language or Visual Basic, or a dynamic programming languagesuch as Python or JavaScript. In some cases, computer program code ormachine-level instructions derived from the computer program code mayexecute entirely on an end user's computer, partly on an end user'scomputer, partly on an end user's computer and partly on a remotecomputer, or entirely on a remote computer or server.

For purposes of this document, it should be noted that the dimensions ofthe various features depicted in the Figures may not necessarily bedrawn to scale.

For purposes of this document, reference in the specification to “anembodiment,” “one embodiment,” “some embodiments,” or “anotherembodiment” may be used to describe different embodiments and do notnecessarily refer to the same embodiment.

For purposes of this document, a connection may be a direct connectionor an indirect connection (e.g., via another part). In some cases, whenan element is referred to as being connected or coupled to anotherelement, the element may be directly connected to the other element orindirectly connected to the other element via intervening elements. Whenan element is referred to as being directly connected to anotherelement, then there are no intervening elements between the element andthe other element.

For purposes of this document, the term “based on” may be read as “basedat least in part on.”

For purposes of this document, without additional context, use ofnumerical terms such as a “first” object, a “second” object, and a“third” object may not imply an ordering of objects, but may instead beused for identification purposes to identify different objects.

For purposes of this document, the term “set” of objects may refer to a“set” of one or more of the objects.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A method for operating a data management system,comprising: acquiring a first full image snapshot and a first set ofincremental files associated with a first set of versions of a real orvirtual machine from a computing device; storing the first full imagesnapshot and the first set of incremental files associated with thefirst set of versions of the real or virtual machine; transferring thefirst full image snapshot and the first set of incremental filesassociated with the first set of versions of the real or virtual machineto an archival source; acquiring a second set of incremental filesassociated with a second set of versions of the real or virtual machinefrom the computing device; detecting that a data size corresponding withthe first set of incremental files and the second set of incrementalfiles has exceeded a threshold data size; generating a second full imagesnapshot corresponding with a second version of the second set ofversions of the real or virtual machine in response to detecting thatthe data size corresponding with the first set of incremental files andthe second set of incremental files has exceeded the threshold datasize, the generating the second full image snapshot includes applying atleast a subset of the second set of incremental files and the first setof incremental files to the first full image snapshot; storing thesecond full image snapshot corresponding with the second version of thereal or virtual machine; and transferring the second full image snapshotto the archival source.
 2. The method of claim 1, further comprising:detecting that ages associated with the first full image snapshot andthe first set of incremental files have exceeded a threshold age andtransferring the first full image snapshot and the first set ofincremental files to the archival source in response to detecting thatthe ages associated with the first full image snapshot and the first setof incremental files have exceeded the threshold age; and transferringan instruction to the archival source to delete the first set ofincremental files subsequent to transferring the second full imagesnapshot to the archival source.
 3. The method of claim 1, furthercomprising: detecting that generating the second full image snapshotdoes not cause the data management system to concurrently generate morethan a threshold number of full image snapshots; and the generating thesecond full image snapshot includes generating the second full imagesnapshot in response to detecting that the data size corresponding withthe first set of incremental files and the second set of incrementalfiles has exceeded the threshold data size and detecting that generatingthe second full image snapshot does not cause the data management systemto concurrently generate more than the threshold number of full imagesnapshots.
 4. The method of claim 3, wherein: the detecting thatgenerating the second full image snapshot does not cause the datamanagement system to concurrently generate more than the thresholdnumber of full image snapshots includes accessing a distributedsemaphore for limiting the number of full image snapshots concurrentlygenerated by the data management system.
 5. The method of claim 1,further comprising: detecting that an amount of disk space for storingthe first set of incremental files and the second set of incrementalfiles has exceeded a threshold amount of disk space and generating thesecond full image snapshot in response to detecting that the amount ofdisk space for storing the first set of incremental files and the secondset of incremental files has exceeded the threshold amount of diskspace.
 6. The method of claim 1, further comprising: detecting that thecombined file sizes of the first set of incremental files and the secondset of incremental files has exceeded a threshold data size andgenerating the second full image snapshot in response to detecting thatthe combined file sizes of the first set of incremental files and thesecond set of incremental files has exceeded the threshold data size. 7.The method of claim 1, further comprising: detecting that the combinedfile sizes of the first set of incremental files and the second set ofincremental files has exceeded a threshold fraction of a file sizecorresponding with the first full image snapshot and generating thesecond full image snapshot in response to detecting that the combinedfile sizes of the first set of incremental files and the second set ofincremental files has exceeded the threshold fraction of the file sizecorresponding with the first full image snapshot.
 8. The method of claim1, further comprising: detecting that the combined file sizes of thefirst set of incremental files and the second set of incremental filesis greater than half the file size of the first full image snapshot andgenerating the second full image snapshot in response to detecting thatthe combined file sizes of the first set of incremental files and thesecond set of incremental files is greater than half the file size ofthe first full image snapshot.
 9. The method of claim 1, furthercomprising: detecting that the archival source does not have access tocompute resources and generating and transferring the second full imagesnapshot to the archival source in response to detecting that thearchival source does not have access to compute resources.
 10. Themethod of claim 1, wherein: the archival source comprises one of ahardware data storage device, a storage area network storage device, anetworked-attached storage device, or a cloud-based data storagerepository.
 11. A data management system, comprising: a networkinterface configured to acquire a first full image snapshot and a firstset of incremental files associated with a first set of versions of areal or virtual machine; and one or more processors configured to detectthat ages associated with the first full image snapshot and the firstset of incremental files are more than a threshold age and cause thefirst full image snapshot and the first set of incremental filesassociated with the first set of versions of the real or virtual machineto be transferred to an archival source, the network interfaceconfigured to acquire a second set of incremental files associated witha second set of versions of the real or virtual machine, the one or moreprocessors configured to detect that a data size corresponding with thefirst set of incremental files and the second set of incremental fileshas exceeded a threshold data size and generate a second full imagesnapshot corresponding with a second version of the second set ofversions of the real or virtual machine in response to detection thatthe data size corresponding with the first set of incremental files andthe second set of incremental files has exceeded the threshold datasize, the one or more processors configured to patch the first set ofincremental files and at least a subset of the second set of incrementalfiles to the first full image snapshot, the one or more processorsconfigured to cause the second full image snapshot corresponding withthe second version of the second set of versions of the real or virtualmachine to be transferred to the archival source subsequent togeneration of the second full image snapshot.
 12. The data managementsystem of claim 11, wherein: the one or more processors configured tocause an instruction to be transferred to the archival source to deletethe first set of incremental files and the at least the subset of thesecond set of incremental files subsequent to the second full imagesnapshot being transferred to the archival source.
 13. The datamanagement system of claim 11, wherein: the one or more processorsconfigured to generate the second full image snapshot in response todetection that the data size corresponding with the first set ofincremental files and the second set of incremental files has exceededthe threshold data size and detection that generating the second fullimage snapshot does not cause the data management system to concurrentlygenerate more than a threshold number of full image snapshots.
 14. Thedata management system of claim 13, wherein: the one or more processorsconfigured to access a distributed semaphore for limiting the number offull image snapshots concurrently generated by the data managementsystem and detect that generating the second full image snapshot doesnot cause the data management system to concurrently generate more thanthe threshold number of full image snapshots using the distributedsemaphore.
 15. The data management system of claim 11, wherein: the oneor more processors configured to generate the second full image snapshotin response to detection that the amount of disk space for storing thefirst set of incremental files and the second set of incremental fileshas exceeded a threshold amount of disk space.
 16. The data managementsystem of claim 11, wherein: the one or more processors configured togenerate the second full image snapshot in response to detection thatthe combined file sizes of the first set of incremental files and thesecond set of incremental files has exceeded the threshold data size.17. The data management system of claim 11, wherein: the one or moreprocessors configured to generate the second full image snapshot inresponse to detection that the combined file sizes of the first set ofincremental files and the second set of incremental files has exceeded athreshold fraction of a file size corresponding with the first fullimage snapshot.
 18. The data management system of claim 11, wherein: theone or more processors configured to generate and transfer the secondfull image snapshot to the archival source in response to detection thatthe archival source does not have access to compute resources.
 19. Thedata management system of claim 11, wherein: the archival sourcecomprises one of a hardware data storage device, a storage area networkstorage device, a networked-attached storage device, or a cloud-baseddata storage system.
 20. One or more storage devices containingprocessor readable code for programming one or more processors toperform a method for operating a data management system, the processorreadable code comprising: processor readable code configured to acquirea first full image snapshot and a first set of incremental filesassociated with a first set of versions of a virtual machine from acomputing device; processor readable code configured to store the firstfull image snapshot and the first set of incremental files associatedwith the first set of versions of the virtual machine; processorreadable code configured to detect that the first full image snapshotand the first set of incremental files have exceeded a threshold age andtransfer the first full image snapshot and the first set of incrementalfiles to an archival source in response to detection that the first fullimage snapshot and the first set of incremental files have exceeded thethreshold age; processor readable code configured to acquire a secondset of incremental files associated with a second set of versions of thevirtual machine from the computing device; processor readable codeconfigured to detect that a combined data size associated with the firstset of incremental files and the second set of incremental files hasexceeded a threshold data size; processor readable code configured togenerate a second full image snapshot corresponding with a secondversion of the second set of versions of the virtual machine in responseto detection that the data size corresponding with the first set ofincremental files and the second set of incremental files has exceededthe threshold data size; processor readable code configured to generatethe second full image snapshot via patching of the first set ofincremental files and at least a subset of the second set of incrementalfiles to the first full image snapshot; processor readable codeconfigured to store the second full image snapshot corresponding withthe second version of the second set of versions of the virtual machine;and processor readable code configured to transfer the second full imagesnapshot to the archival source subsequent to generation of the secondfull image snapshot.